Sen. George McGovern (D-S.D.), a possible new chairman of the Senate African affairs subcommittee in the new Congress, said yesterday it appeared that the Anglo-American peace initiative in Rhodesia has failed, and that the United States might well "disengage" from Rhodesia now.

Speaking to a breakfast meeting of reporters, McGovern said he was deeply pessimistic about the Rhodesian situation, and added that "the chances of the United States bringing about a peaceful settlement there are shrinking very fast."

McGovern returned last week from an etended tour of southern Africa, during which he met with Rhodesian leaders and officials of nearby countries.

He predicted "a long, bloody struggle" between black nationalists and the Salisbury regime, and expressed doubt that the United States or Britian could head this off.

At the same breakfast meeting, McGovern sharply criticized President Carter's budget and economic policies, and said if Carter refuses to change course, "the most likely result would be that we'll lose to the Republicans" in 1980.

He said he would join other liberals in fighting Carter's budget priorities in the Senate, and in trying to pressure the president to return to "the Democratic mainstream" in time to prevent his defeat at the polls in 1980.

By "disengagement" from Rhodesia, McGovern meant that the United States should acknowledge the failure of its efforts to achieve a negotiated settlement in Rhodesia and accept the fact that there is no further purpose in active American diplomacy in the dispute.

McGovern said that if the United States adopted this posture, the government of Ian Smith in Salisbury and the black nationalist leaders engaged in a civil war against the Salisbury regime might decide that they had to resolve their differences themselves. McGovern said he saw no other plausible scenario to avoid wider civil war.

McGovern said he opposed recognizing the Smith regime, which has been broadened to include some blacks, because the United States retains an obligation to respect decision by the United Nations on Rhodesia. He acknowledged, however, that if the civil war intensifies and Smith continues to make more room for blacks in his government, pressures will mount here and in other western countries to recognize it.

McGovern said he thought the time had come for the United States to recognize the left-wing regime in Angola, even if it continues to rely on Cuban troops and advisers to provide internal security in the former Portuguese colony.

The best way to reduce Angolahs dependence on Cuban and Soviet assistance, McGovern said, would be to offer the Angolans alternatives such as closer economic relations with the West, particularly the United States.

On domestic issues, McGovern accused Carter of following a Republican policy of high interest rates, increased defense spending and lower expenditures on domestic programs. The predicted those policies would produce a recession.

But McGovern said "I still haven't given up on Carter," and he expressed hope the president would adopt a new policy before this proves disastrous. The refused invitations from reporters to say he would support a challenge to Carter from the liberal wing of the Democratic Party.

McGovern said he is uneasy about his own reelection campaign in South Dakota in 1980, and said right-wing opponents have already begun actively to oppose him. But he said it was too late for him to try to abandon his traditional liberalism to win votes.

"If I tried to change now I'd not only be defeated, I'd deserve to be defeated," he said.

McGovern said he has not yet decided whether to seek the chairmanship of the Africa subcommittee of the Senate Foreign Relations Committee, which has become vacant because of the defeat of Sen. Dick Clark (D-Iowa). Associates said later they thought McGovern would take the job.