In his outlook on the world after a year of grappling with its harsh realities, President Carter last night gave Congress a sober accounting, claiming progress for his policies, but recognizing no easy roads ahead.

Carter avoided any explicit comment about the heavy uncertainty suddenly injected this week into the preoccupying region of world tension, the Middle East. But with Secretary of State Cyrus R. Vance about to meet today with Egyptian President Anwar Sadat on the endangered Egyptian Israeli peace talks, Carter stressed his administration's determination "to maintain the momentum of the current negotiations . . ."

"Our role," Carter said bluntly and succinctly, "has been difficult and sometimes thankless and controversial, but it has been constructive and necessary - and it will continue."

Administration officials avoided any comment yesterday that might aggravate the precarious state of negotiations since Sadat withdrew his delegation from the Jerusalem peace talks Wednesday. "We are not going to level blame at anyone," a State Department spokesman said. Other officials refused to acknowledge that there has been a breakdown in the talks, and expressed confidence that the current differences can be overcome.

American officials sidestepped speculation that Sadat's objective may be to induce Carter to call a three-sided summit meeting with Begin, in Washington, try to force a peace settlement.

In Jerusalem, Israeli Prime Minister Menahem Begin told a questioner: "If U.S. President Carter invites me and President Sadat to go to Washington for a meeting, I will respond very willingly and go there." But Begin also said, "Let no one frighten us with this inconceivable concept of pressure to be exerted upon us."

State Department spokesman John H. Trattner said "I know of no present plans" for such a meeting, "or future plans."

Carter told Congress in the message accompanying his State of the Union address last night that "the greatest danger to world peace and stability is not war among the great powers, but war among small nations."

During the past year, he said, the United States has helped "to promote productive negotiations in two troubled regions: the Middle East and Southern Africa. We have also tried to settle conflicts in the Horn of Africa and on Cyprus," he said. But Carter warned anew that the Ethiopia-Somali conflict in the Horn raises "a danger that the Soviet Union and Cuba will commit their own soldiers in this conflict, transforming it from a local war to a confrontation with broader strategic implications."

The Soviet Union, Cuba and Ethiopia all have ridiculed claims that the presence of Soviet and Cuban advisers in Ethiopia may lead into a combat role.

In Latin America, Carter said, the negotiation of two Panama Canal treaties has laid promising groundwork for what he described as the process of "regional reconciliation," and "the world is watching" to see if Congress will confirm those treaties.

The President last night used unusually restrained language in his forecast on completing the centerpiece of American-Soviet negotiations, a new nuclear strategic arms limitation talks accord.

In the fall, Carter spoke of completing the new nuclear pact "in a few weeks," or spoke of an agreement "within sight." Last month, chief U.S. negotiator Paul Warnke said if the present rate of progress in negotiations is maintained, an agreement could be reached "in the next three months."

But Carter, who recently said "I think my biggest mistake has been in inadvertently building up expectations too high," last night employed his most guarded prediction. It was: "If the talks result in an agreement this year - and I trust they will," the accord will enhance world stability and American security.

Carter said the negotiatons "have been difficult and prolonged" because of his administration's determination "to reduce, not just contain," both the numbers of American-Soviet nuclear strategic weapons and qualitative improvements in them.

The President also listed progress in other areas of negotiations with the Soviet Union, including the goal of a total ban on all nuclear weapons tests. He also said "we have decided to cut down our arms transfers abroad," in which the United States embarrassedly stands as the world's "principal arms merchant."