President Carter's first meeting with Soviet Ambassador Anatoliv F. Dobrynin yesterday was overshadowed by the administration's denials that it has backed away from support for human rights in the Soviet Union.

"I told Dobrynin that we're not going to back down on that," the President, in the presence of reporters, told Vice President Mondale as the Minnesotan returned from his global tour.

The President made the remark aboard a helicopter en route from Andrews Air Force Base to the White House when Mondale asked, as accompanying reporters paraphrased it, "if the Sakharov flap had died down . . . "

The exchange was a smapling of the growing concern at the top of the Carter administration over world reaction to U.S. handling of the dispute over nuclear physicist Andrei D. Sakharov, the Soviet Union's leading dissident.

That dispute started with a State Department statement last Thursday cautioning the Soviet Union against attempts "to intimidate" Sakharov. Qualifying statements by the President and Secretary of State Cyrus R. Vance led, in turn, to a widespread impression that the administration was going out of its way to avoid offending the Soviet Union.

As a result, the administration recognized that it faced danger to its credibility, as well as to the basic pattern of its relations with the Soviet Union.

Both the President and Vance attempted to recoup yesterday.

Carter, during the brief helicopter ride, told Mondale in front of reporters that in his meeting earlier in the day with Dobrynin he told the Soviet envoy that his administration has a commitment to human rights.

The President, newsmen reported in paraphrase, said he told Dobrynin that when statements in defense of human rights are made by his administration, it is not an attack on the Soviet Union but an expression of support for the U.S. commitment.

After the 50-minute Carter-Dobrynin talk, White House aides separately underscored that dual theme: the United States would "not back down" on human rights, but it is not launching an attack on the Soviet Union.

The President, however, did not specifically raise the Sakharov case with Dobrynin, it was acknowledged. Instead, the President referred to human rights in general, it was said, and that subject was described as only a small part of the discussion.

Officially the Carter-Dobrynin meeting was described in the usually bland style: "They had a useful exchange of views reviewing the whole range of U.S./Soviet relations, with particular emphasis on the forthcoming SALT (strategic arms limitation talks) negotiations."

Vance, who is scheduled to go to Moscow in late March to lay the groundwork for reopening the stalemated nuclear strategic arms talks, participated in the meeting with Dobrynin, as did Zbigniew Brzezinski, the President's national security affairs adviser.

Neither before nor after the meeting was there any sign of tension, and a White House aide said the private talk was similarly "cordial."

The President, chatting with Dobrynin at the outset while reporters and photographers were present, said, "I hope to form a very close relationship with you and also with Mr. Brezhnev (Soviet Communist Party leader Leonid I. Brezhnev)."

The Soviet ambassador brought a set of wooden dolls for the Carters' daughter, Amy. Other gifts included a miniature samovar for the President.

"I have heard great things about you and your service in Washington," Carter told the veteran envoy, who has been based here since 1962. Dobrynin said the two nations have many mutual interests "and we must not let them go by."

At the State Department, Vance, through a spokesman, similarly sought to counter interpretations that the United States had "backed down" from its original outspokenness in the Sakharov statement - issued without Vance's clearance. It was Dobrynin who first brought the statement to Vance's attention, by protesting it, last Thursday.

At a press conference on Monday Vance said that the United States will "speak frankly about injustice . . . from time to time," but without being "strident or polemical."

That statement was interpreted by numerous listeners as another example of the administration's intention to soften the impact of the department's original statement.

On Sunday, Carter emphasized that neither he nor Vance had seen the statement in advance. The President also said then that "we are not going to back down," but in addition he said "(we) don't want to aggravate problems of this kind."

State Department spokesman Frederick Z. Brown said yesterday, on behalf of Vance: "I think it's not correct to draw the conclusion . . . that there is any lessening of the commitment of this administration on human rights questions."

Department officials privately said they were disturbed by domestic and foreign reports to the effect that the Carter administration "blinked" in its first encounter with the Soviet Union. Accounts have pyramided as they circulated around the world. One Yugoslav broadcast, for example, said incorrectly: "President Carter described the State Department's statement on Soviet phsicist Sakharov as foolish lecturing of foreign governments . . ."

Initially, administration officials hoped they had only "a small foul-up" on their hands. Instead, they face the almost certain prospect that when Vance does go to Moscow in March, he still will be asked questions about Sakharov.