Secretary of State Cyrus R. Vance presented his version of a "positive" and "constructive" U.S. foreign policy to the House International Relations Committee yesterday, and said that he was speaking for President Carter.

Several members of the commitee, however, said they found it hard to square Vance's rendition with tough anti-Soviet declarations by presidential assistant Zbigniew Brzezinski as well as some recent statements by Carter.

In a 10-page written statement and nearly two hours of public testimony, Vance sought to dispel uncertainty and apprehension about U.S.-Soviet relations and African policy. While conceding that last weekend's comprehensive and highly unusual Soviet denunciation of U.S. policy contained "some very tough words," Vance said that "the door was clearly left open to continue to pursue cooperative measures" and expressed belief that the Russians - as well as the United States - wish to seek arms control agreements and detente.

Vance promised a more extensive U.S. response in a few days to the lengthy Soviet document. "I would only say at this time that the most constructive course for both countries as we move ahead would be to concentrate on the concrete actions we both can take to reduce tensions and to reach agreement on the critical issues now under negotiation."

Rep. Dante Fascell (D-Fla.), one of the moving forces behind the recent letter from the House commitee to Carter complaining of "confusion and doubt" about U.S. foreign policy, expressed the belief that the administration tried to launch a major change in international strategy without prior consultation with Congress. Mentioning White House national security affairs adviser Brzezinski Fascell told Vance that discordant signals from the government raised questions of "who's got the president's right ear?" and "are we going toward a heightened Cold War rhetoric?"

As he sees it, Fascell declared, "Brzezinski used a two-by-four [on the Russians], the president said 'not that hard, just hard enough to let them know we're alive,' and the secretary of state said, 'we are conducting our normal programs.'"

Vance replied that he had been designated to make the policy clear. He put the blame for rising tensions on developing circumstances, saying that "over the last several weeks there have been a number of events in Africa which have focused attention and caused concern about what are Cuban and Soviet intentions." He added in cautious and lawyerlike fashion that each situation has to be analyzed on its own, case by case.

The best course of action, Vance declared, is "a positive course" which could result in decisions by various African nations on their own to ask Cuba and the Soviet Union to withdraw and which could create circumstances making the presence of outsiders no longer justifiable.

Vance passed up a number of opportunities to comment on Brzenzinski in response to congressional remarks, including the statement by Rep. Don Bonker (D-Wash.) that "I'd feel a lot better if the State Department and not the National Security Council had the prevailing voice in foreign policy decisions." In an allusion to the House committee's request to Carter for an appearance by Vance "or whoever you determine is best able" to explain recent developments, Vance stated that "I speak for the president as well as myself."

Vance's statement was to some extent his counterpart of the June 7 Carter speech at the U.S. Naval Academy, penned by the president himself during a Camp David weekend and cleared without much change by his senior advisers. Vance began writing his statement to the committee during a long trip home from London Saturday and sent the last of several drafts to Carter at the White House Sunday afternoon. Carter "made a few changes and agrees with it completely," said Vance.

Although Vance's statement referred several times to Carter's Annapolis address as a touchstone of policy, the differences in stress and tone between the two documents was notable. Vance did not repeat Carter's much-headlined challenge to the Soviet leaders to choose "either confrontation or cooperation," but said in muted terms that "both sides will continuously be making choices between an emphasis on the divergent elements of our relationship, and an emphasis on the cooperative ones." Vance said that Carter had "made clear" at Annapolis that the U.S. prefers to broaden the areas of cooperation.

The secretary of state made no mention of Brzenzinski's statements that Soviet-Cuban activities in Africa could imperil strategic arms limitation talks, nor Carter's more restricted statements that tensions between the superpowers could complicate the ratification process for a SALT agreement.

"When we reach an agreement that maintains and enhances our security and that of our allies, and is adequately verfiable, we will sign it." Vance said simply. Asked to confirm absolutely that there is no "linkage" between Africapolicy and SALT negotiations, Vance responded. "That is correct."