Every President who reaches for an agreement with the Soviet Union on nuclear arms control takes on two sets of negotiations - one with the Kremlin, and another with his own government.

Among arms control specialists, it is often said that the "internal negotiations" can be more difficult than the "external negotiations," for both the United States and the Soviet Union.

To purists, the comparison is overdrawn. But it evidently stands high in the mind of President Carter as a danger to avert. He has pointed to the dissent inside the Ford administration and the presidential election, as the principal reasons for Ford's inability to conclude a strategic arms limitation talks (SALT) treaty with the Soviet Union.

In private, many Ford administration insiders go much further than that. The former President sources on both sides of his SALT impasse say, was outmaneuvered inside the government.

Ford was caught between two conflicting priorities: his campaign for nomination against Ronald Reagan vs. a SALT II accord to complete the nulcear agreement he made with Soviet leader Leonid I. Brezhnev at Vladivostok in November, 1974.

In effect, Ford was compelled to sacrifice one objective for the other. He defeated Reagan for the Republican nomination. But in moving to the right of the political spectrum, to compete with Reagan for right-wing votes, Ford became a gostage to the opponents of a SALT compromise that Secretary of State Henry A. Kissinger implored him to make.

The opposition - the Defense Department and its allies in government and in the Congress - was not passive about the President's dilelmma. Nor was Kissinger.

Kissinger told the President he needed only "to spill a little (bureuacratic) blood" to reach the SALT compromise, sign it at the long-projected Washington summit conference with Brezhnev, and carry it into the November election as a foreign policy triumph.

The internal clash reached a peak in January-February, 1976, the most sensitive political period for Ford, after Kissinger returned from Moscow in January urging a compromise. Reagan was beginning his attack on the Ford-Kissinger foreign policy, heading into the nation's first primary election, in New Hamphire Feb. 24.

Kissinger's opponents on SALT made sure the President recognized the political consequences of following Kissinger's advice: If the Pentagon was overruled on SALT, that was bound to "leak out," exploding against Ford in the primary campaign.

There was nothing so bald as a direct threat to the President. Said one Kissinger opponent, drily, "It was all done within the system."

Ford, as a consequence, sided with kissinger's opponents in February. he sent Moscow what both sides describe as a "hang tough" reply to the proposel that Kissinger brought from Moscow.

The negotiations virtually froze.

After Ford won the Republican nomination in August, he pushed for a SALT compromise to recoup his earlier hopes. It was too late; by then even some of the strongest SALT supporters opposed a last-minute rush for agreement just before the November election.

In retrospect, the former President is reported by some sources to wish he had forced through a SALT compromise, over the internal opposition. Whether Ford would still occupy the White House if he had done so is anyone's guess. Beyond question, the 1976 election campaign would have been considerably different.

Each President who negotiates with the Soviet Union must decide how he will deal with his own bureaucracy. Bargain with it? Overrule it? Circumvent it?

No consensus automatically springs up over nuclear strategy. Experts can disagree strongly about what is prudent and what is perilous. The ultimate choices, therefore, are political decisions.

There were long roots to the dispute that frustrated President Ford's SALT ambitions. Some of them have entangled Paul C. Warke, Carter's nominee for director of the Arms Control and Disarmament Agency and chief SALT negotiator.

Former President Nixon and Kissinger, then at the White House, conducted the SALT I negotiations in extraordinary secrecy. "Back channels" were used to communicate to the Kremlin, behind the back of U.S. negotiators, and sometimes without knowledge of the Secretaries of State and Defense.

The suspicions that developed afterward, coupled with charges that Kissinger had made lopsided concessions to the Russians in 1972, converged in the decisive opposition to Kissinger's negotiations on SALT II.

In one tradeoff after SALT I, to try to help ease the path for SALT II, Nixon sought to make peace with Sen. Henry M. Jackson (D-Wash.), Kissinger's prime challenger. Nixon agreed to divide the post of arms control director and chief SALT negotiator, and put harder-line negotiators on SALT.

In addition, the arms control agency itself was stiffened, with officials holding a sterner view of the Russians moved in to replace more ardent arms control champions. That "purge" had unintended consequences. It helped to convert the arms control agency into a Pentagon ally against Kissinger in 1976.

Another tradeoff of 1972 had greater repercussions four years later.

To enlist support of the Joint Chiefs of Staff for ratification of the 1972 nuclear agreements, Nixon obtained a major increase in weapons research and development funds.

One project was long-range cruise missiles, which the Pentagon was prepared to drop in 1973. (The cruise missile, is, in effect, an unmanned, low-flying jet with a range up to 2,000 miles.) Kissinger urged the military to continue primarily to save cruise missiles as a future "bargaining chip" with the Russians. Instead, cruises missiles turned into the most confounding obstacle for Kissinger's attempt to resolve the SALT II treaty.

Cruise missiles, and the Soviet bomber system known in the West as Backfire, became the principal obstacles to a new agreement.

Two major nuclear agreements had been signed at Moscow in 1972. For the first time, adversary nations agreed to ban national defense systems, exposing themselves to attack from each other with intercontinental missiles. This was the Anti-Ballistic Missile Treaty, a major breakthrough, little-disputed.

Virtually all subsequent argument centers on the complementary side of the process - controls on offensive strategic weapons. A five-year accord was signed in 1972; it runs out Oct. 3 of this year. Its replacement is the Ford-Brezhnev Vladivostok accord, to run until 1985.

In 1972 the Russians ere racing to catch up with previous American superiority, and had taken the lead in numbers of intercontinental missile launchers. The SALT I "freeze" on missile launchers left the Russians with superior numbers of strategic wissiles launched from land or sea, a maximum of 2,358 to 1,710 for the United States. The United States had, and retains, the advantage in nulcear warheads, with its muliple-warhead missiles and a larger fleet of intercontinental bombers.

Kissinger and other administration officials maintained that the agreement was balanced, with the United States behind in missile launchers but ahead in warheads, bombers and technology. Critics contended that the Russians, with more and larger missiles, eventually could duplicate the mulitple warheads and other technology, and gain military superiority.

The ratification of the SALT I Accords moved the argument to SALT II. At-Vladivostok, Kissinger said, any imbalance was wiped out by agreement on similar numbers of strategic delivery systems on both sides, with "important concessions" by the Soviet Union.

An equal ceiling of 2,400 American and Soviet intercontinental missiles and bombers was set, of which 1,320 could have multiple warheads. Ford hailed this as "a cap" on the arms race.

The debate only shifted direction Critics on right and left assialed the celing as far too high. Then "the cap" began oozing from the two sides, in the new dispute over Soviet Backfire bomber and American long-range cruise missiles, both omitted from the Vladivostok discussions.

The Joint Chiefs of Staff insisted that the Backfire can operate as a long-range bomber against targets in the United States, and should be counted as strategic. The Soviet Union maintained that Backfire is a medium bomber, outside the Vladivostok limits.

Positions are reversed on long-ranged cruise missiles. As non-ballistic missiles, the United States claimed, they were exempt from the Vladivostok ceilings. The Soviet Union originally sought to ban all cruise missiles beyond 600 kilometers, or 373 miles, the range of existing Russian types.

Long-range curise missiles, with accuracy precise enough to hit a selected building ("You can shoot it down a pickle barrel at 2,000 miles," Reagan exclaimed during the elction campign), are claimed to cost only about a tenth as much as ballistic missiles. Because they can carry nuclear or non-nuclear warheads, and serve as a strategic or tactical weapons, they also raise great problems of distinguishing which is which.

Kissinger and his supporters regarded the Backfire and cruise missiles, as one source expressed it last week, as "far out on the margin of strategic significance."

Privately, even some Kissinger critics agree. The military services themselves are divided about roles and missions for curse missiles. But the controversy solidified Kissinger's critics in the different camps, especially advocates of cruise missiles, who see intermediate-range cruise missiles as a major offset to Soviet power in Europe, and "a great equalizer" against the Russians at sea.

Kissinger was ready to trade about 250 Backfire bombers with Soviet pledges of limitation on their use for an equal number of long-range cruise missiles on ships, both outside the Vladivostok ceilings; to count bombers with 1,500-mile cruise missiles as multiple-warhead weapons, and to ban long-range cruise missiles on submarines.

Critics assailed that mix as unbalanced in Soviet favor and Soviet assurances on Backfire as unacceptable.

The opposition to Kissinger was led by the Joint Chiefs of Staff. They were supported by Defense Secretary Donald H. Rumsfeld, President Ford's longtome confidant, recently arrived at the Pentagon to replace ousted James R. Schlesinger. Ford's summary firing of Schlesinger, widely misconstrued as a victory for Kissinger, had infuriated the Republican right-wing, and that was already troubling Ford's election advisers.

Kissinger was without allies beyond the State Department and the National Security Council staff. The arms control agency, semi-autonomous in the State Department and largely ignored by Kissinger, joined the opposition, with mild-mannered director Fred C. Ikle encouraged by his deputy, John F. Lehman, Jr., to speak out.

Lehman, although a onetime member of Kissinger's NSC staff, was championing cruise missiles. So was Lehman's close friend, Richard Perle, a nuclear specialiest for Sen. Jackson and one of the most effective Kissinger critics in Washington.

Perle recently said that, compared to "the resources Henry had at his disposal," the opposition's resources "were trivial." "I could talk to people one at a time," Perle said; "Henry had a whole planeload [of reporters] and the stories went all over the world." The problem, however, Perle insists, was not internal disagreements, but Soviet intransigence.

Nevertheless "the key factor was the election," said a central particupant, and numerous others agree. If President Ford had supported Kissinger, this source said, "It very soon would have come out that Defense had been overruled."

In place of the compromise Kissinger sought, the counter that went back to the Russians, in several variations, was an offer to proceed with the original portions of the Vladivostok accords and to bypass the Backfire and cruise missile controversy for subsequent negotiations.

Kissinger argued that the Soviet Union would reject that out of hand (which it did) because it left the more dynamic weapons system, cruise missiles, unconstrained. His critics charged that Kissinger undermined the counterproposal, and failed to press it forcefully.

Basically this is the same offer that President Carter now has made to the Soviet Union publicly and privately. Is there any reason to expect the Soviet Union to accept this approach which they previously rejected? Carter administration sources maintain there is.

There are numerous ways to set aside the Backfire-cruise missible dispute, in a form more equitable to the Soviet Union. A slowdown or limit, or both, on cruise missile development is an obvious approach, suggested by many outside specialists.

Carter administration strategists say they believe the Soviet Union is eager to reach a SALT II accord before te Oct. 3 deadline, and then move into SALT III negotiations on arms reductions as Carter has urged.

The Carter administration believes it has a good prospect for avoiding the internal splits that plagued the Ford administration's nuclear stratgey, with Harold Brown at Defense, Cyrus R. Vance at State, Zbigniew Brezinski as national security adviser, and Warnke as chief SALT negotiator.

By his unusual public, and private, emphasis on arms control, these sources say, the President has aroused Soviet interest for "locking in" his administration to continuing negotiations.

Carter already has spent on unprecendented amount of time for a new President inprivate discussions with the Joint Chiefs of Staff. He also has struck sparks of parallel interest with Sen. Jackson and other Kissinger critics.

The President "is determined that people get a fair hearing," said one insider; "they don't have to go to the Hill to get an argument raised."

But, the insider added, President Carter "has made it clear that he is going to make the decisions."

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