President Reagan's claim that "we have resumed our historic role as a leader of the free world" was the foreign policy highlight of a State of the Union address that emphasized legislative battles on Capitol Hill rather than diplomatic and military struggles in the rest of the world.

Reagan's three priorities in last night's speech were the embattled MX missile, which is clinging to life by a thread in Congress; covert U.S. aid to armed antigovernment rebels in Nicaragua, which was rejected by the lawmakers again last October, and the "Star Wars" plan to stop incoming enemy missiles, which is controversial on Capitol Hill and may be difficult to sell as the costs pile up and the months pass.

The MX missile, which Reagan has dubbed "the peacekeeper," was saved in the Senate last June by the tie-breaking vote of Vice President Bush.

Last night Reagan called coming votes on the issue this spring "a critical test of our resolve" to back up the U.S. arms negotiators who soon will be sitting across from their Soviet counterparts at the bargaining table in Geneva.

Reagan spoke more obliquely than he has in the past of the covert U.S. aid to the Nicaraguan "freedom fighters," or "contras." While saying the United States "must not break faith" with anti-Soviet insurgents, he did not specifically call for Congress to restore the Nicaraguan covert aid program.

A senior administration official who briefed reporters at the White House last night refused under heavy questioning to say whether Reagan will ask for reestablishment of the covert program rejected by the lawmakers.

The administration reportedly is considering alternatives in view of assertions by influential Republicans as well as Democrats on Capitol Hill that the contra aid program is dead.

Reagan said in his speech that "support for freedom fighters is self-defense and totally consistent with the OAS Organization of American States and U.N. charters." Critics said, however, that only announced self-defense plans -- and not secret enterprises -- are acceptable under the international charters.

The president emphasized that he views the Strategic Defense Initiative, popularly known as Star Wars, as "the most hopeful possibility of the nuclear age."

The research program to destroy nuclear missiles in flight is a personal initiative of Reagan that was sprung on the rest of his administration with little warning on March 23, 1983.

The president said nothing about the plan in last year's State of the Union address, but since the November election it has taken on increasing prominence -- and a central role in the declared U.S. "strategic concept" for the arms negotiations.

MX, contras and Star Wars seem to have been given special attention last night because they are among the few aspects of Reagan's global policies that are in trouble, or seem headed for trouble, in Congress. His broader diplomatic and military policies in the world, which seem more conventional and widely accepted than they did in his first years as president, are enjoying a respite from attack at home and abroad.

Underlying his ebullient tone was the landslide in November, which created a strong diplomatic as well as domestic position for Reagan as he started "four more years."

His sweeping victory doubtless played a role in the Soviet Union's decision to return to the nuclear-arms bargaining table on something close to U.S. terms, a procedural triumph rather than a substantive one but a clear success for Reagan's policies as a long, hard set of negotiations begins.

That same overwhelming mandate from U.S. voters has prompted foreign leaders from every corner of the globe to line up for visits to the Oval Office. But as difficulties with Australian Prime Minister Robert Hawke over MX testing illustrate, an invitation to the White House does not guarantee smooth sailing for U.S. foreign policy.

Reagan made no reference in his address to the situation in Lebanon, which was prominent in last year's State of the Union address.

He declared then, "We are making progress in Lebanon" and insisted that "we must not be driven from our objectives for peace in Lebanon by state-supported terrorism."

The day after making that address, it later came to light, Reagan approved a plan to remove the U.S. Marines from Beirut.

The U.S. withdrawal was announced Feb. 7, one year ago today.

The pullout created shock waves through the Middle East as the high-profile U.S. commitment was suddenly abandoned. But it relieved the anxiety on Capitol Hill and among the American public and contributed to smooth sailing for Reagan's reelection campaign.

At one stage of preparation, last night's address was to contain a paragraph reaffirming U.S. determination to work for peace in the Middle East and calling for peaceful pursuits by the nations of the area. This was dropped in the final draft, leaving the speech without mention of the difficulties in that region.

In the international economic area, Reagan announced that he is calling for a start in the coming year on a new round of global trade negotiations. He mentioned the plan in last year's State of the Union but was a bit more explicit this time about a possible starting time. So far, despite his efforts at last June's London summit, the other industrialized nations have not agreed to a date for the new round.

Reagan did not cite details to back up his claim that the United States has "resumed" its historic leadership role. White House aides cited the start of a shift in the military balance between the United States and Soviet Union, a resurgent U.S. economy and "a restored foundation of deterrence" against Soviet actions in the Third World as the basis for Reagan's statement.