On the seventh floor at the State Department, the Operations Center was playing to capacity.

Never before had Carter administration officials had so many working groups going at once. One monitored the crisis in Iran. Another had Afghanistan. A third watched Chad. The Indochina hands had to monitor their war from downstairs, the center was so crowded.

To outsiders, it had begun to seem like all the groups were working but the policies were not.

And President Carter and his advisers were aware of these concerns as they rode Air Force One back from the Mexico summit, which they knew by then had fared poorly in the American television and press.

During that flight 10 days ago, the president, Secretary of State Cyrus R. Vance, national security affairs adviser Zbigniew Brzezinski and communications adviser Gerald Rafshoon began discussing what to do about Carter's next major undertaking, a speech at Georgia Tech that was to be his first full defense of the strategic arms limitation treaty (SALT II).

The speech was already written. It had been sent to the traveling White House from the real White House the day before, and the president and his advisers thought it was good.

But Carter and his advisers came to the conclusion that the president could not very well talk only about the importance of approving a new SALT agreement with the Soviets, while glossing over the facts that: in Afghanistan, the American ambassador had just been killed (with involvement of Soviet advisers, U.S. officials say), the American embassy had been surrendered to communist attackers in Iran (where Soviets, via radio, are trying to foment unrest, U.S. officials say); and in Indochina, the Sino-Vietnam war threatened to bring the Soviets into the struggle in defense of their client-allies in Hanoi.

Another factor that they recognized, according to several presidential aides, was that Carter and his policies were being criticized as weak, vacillating and ineffective -- and that the events of this one week in February were likely to fuel the critics.

Said one presidential aide: "Obviously we felt that we have got to show that ours is a consistent and well-though-out policy -- despite these charges that we are a weak,helpless giant and that we don't know where we are going."

And another explained: "The idea was to put all of those events into perspective. It was not to do a muscle-flexing and tough-guy speech. Thank God Jimmy Carter does not feel the need to pump iron in his foreign policy."

So it was that the president's speech at Georgia Tech last Tuesday was transformed into a major statement of U.S. foreign policy (drafted by Brzezinski and his staff, in consultation with Vance and his). Two days later, Carter gave a repeat performance -- his statements slightly refined and sharpened -- to a group of editors and broadcasters meeting at the State Department.

The theme of both speeches was that, in a world undergoing rapid and at times turbulent change, there are real limits to the use of American power.

Carter spoke of Iran.

"Those who argue that the United States should or could intervene directly to thwart these events are wrong about the realities of Iran," he said in his Georgia speech. Yet he also had a firm warning: "If others interfere directly or indirectly, they are on notice that this will have serious consequences and will affect our broader relationship with them."

(Presidential officials make it clear that Carter was talking here about the Soviets, who they say have tried to disrupt events in Iran through radio broadcasts. The United States will not retaliate by linking Iran to the SALT pact, they say, but there are other means of demonstrating U.S. concern. During the trial of Soviet dissident Anatoly Scharansky, for example, visits of U.S. officials to the Soviet Union and U.S.-Soviet commercial trade projects were postponed by the Carter administration).

Carter also spoke of Indochina: he said the Chinese invasion of Vietnam was "as a result" of the Vietnamese invasion of Cambodia. This, officials stress, was not meant as a justification for the Chinese action, which the Carter administration officially opposes and says it tried to forestall.

Here, too, Carter had a warning: the United States is concerned that the conflict will widen "with unforeseen and grave consequences for the nations in the region and beyond," he said. Officials say this was a reference to the danger of Soviet intervention in behalf of Vietnam. The United States, Carter said, is "fully prepared to protect our vital interests wherever they may be challenged." He did not elaborate.

The president emphasized that he will press for approval of a SALT agreement regardless of what happens in places of tumult. SALT is needed even more in times of crisis and U.S.-Soviet competition, he said, because it is then that competition in strategic nuclear arms becomes "inevitable."

Taken together, one Carter senior adviser said, the Georgia Tech speech and the State Department appearance had "some elements of counterattack" against critics urging a greater show of strength in dealing with these crises.

The speeches were designed to portray the Carter policy as one of strength but not one of Mayaguez. "We could have precipitated dramatic action" in Iran, one senior presidential assistant said "... But I don't think you eill find anyone who was close to that process who believes now that those sorts of actions would have been wise."

Another senior presidential assistant cited, as an example of the effectiveness of a firm but lower-key approach, the case of Sgt. Kenneth L. Kraus. He was the Marine guard at the embassy in Iran who was wounded during the siege and later abducted from his hospital bed by the forces of Ayatollah Ruhollah Khomeini, who threatened to bring him to trial on unspecified charges, but who finally released him after strong intercession by Carter.

"If the president had walked out and made a harsh demand, Khomeini would have felt he had to hold him to show the U.S. couldn't push him (Khomeini) around," said the Carter assistant. "So we worked to get him released and we succeeded. But we can't even beat our chests about it now, because we may have to use the same channel. We may have to do it again."

Over at the Carter White House these days, a new attitude seems to have set in among the inner circle. They talk about the political fortunes of their leader like battle-hardened veterans who have seen enough action to know to build their defense lines even before the enemy fires. They specialize now in fortified trenches, built on a new foundation of cynicism and reality, as they await the next round.

One senior presidential adviser says he could see days ago that "everything was ripe" for a new wave of criticism of Carter -- that he is weak, indecisive, ineffectual, and the rest. One Carter aide talks of having felt "media-burn in Mexico," saying that the U.S. media made the Mexican president's toast sound harsher than it was, and made more out of Carter's bathroom humor rejoinder than they should have, and in all wrote negatively about a successful summit.

Another says that Iran "is being used as a cover for anyone who wants to take a shot at us... We knew that on Iran there was going to be a lot of finger pointing."

They say, several of them, that "we have been through this before" -- for example, before the Camp David summit. And they say they will ride it out successfully once again.

Their attitude is not as bitter or angry as it was in other times of bad tidings. Instead, they say, as one senior assistant did, "You work hard, you pursue your policy, and hope for a little luck."

And another gets downright philosophical about it all as he says quietly, "It may be that in the final analysis a good conscience will be the only reward."