With little apparent forethought about the possible international implications, Vice President Mondale has agreed to speak at a luncheon honoring two of the Soviet Union's most controversial dissidents.

Mondale is to be the featured speaker Sunday when the Anti-Defamation League awards its Joseph Prize for Human Rights to Andrei Sakharov and Anatoly Scharansky.

Scharansky, currently in a Soviet prison, has been accused by an official government newspaper of being a CIA agent, and there have been suggestions he may be tried for treason. Sakharov, a leading dissident spokesman, is a Nobel peace prize winner who was not allowed to leave the country to accept the prize.

The Soviet goverment is extremely sensitive about both men, and Mondale's appearance at a luncheon to honor them is likely to rekindle tension over the human rights policies of the Carter administration.

But that apparently was not a significant factor in the largely personal decision by the Vice President to accept the invitation. Mondale is a long time personal friend of Burton Joseph, who established the award in memory of his parents, the late I.S. and Anna K. Joseph.

Richard Moe, Mondale's chief of staff, did not know about the luncheon appearance until it showed up routinely in the Vice President's advance schedule. According to Jerrold Schecter, press spokesman for the National Security Council, the NSC was not consulted about the appearance or the likely Soviet reaction.

"I don't think he regarded it as a particularly serious problem," said Albert Eisele, Mondale's press secretary.

Mondale's decision to accept the invitation comes after months of relative quiet on the human rights front, the result of an apparently deliberate decision by the adminstration to tone down its early rhetoric on the subject.

In February, the President responded to a letter from Sakharov with rights is a central concern of my administration."

"You may rest assured that the American people and our government will continue our firm commitment to promote respect for human rights not only in our own country but also abroad," he said.

The President's letter, and Sakharov's release of it in Moscow, was one of several strains on relations between the United States an the Soviet Union in the first months of the Carter administration.

Mondale was active in the early human rights initiatives. For example, when another Soviet dissident, Vladimir I. Bukovsky, visited the White House in March, he saw Carter only, briefly, spending most of his time with Mondale. The White House, even then attempting to cool its stress on Soviet rights, allowed Bukovsky to be photographed with Mondale but not with the President.

After the months of comparative silence, Mondale's decision to speak at a luncheon where he will be expected to praise Sakharov and Scharansky could be interpreted as a deliberate move to revive the administration's early fervor on the human rights issue. But, according to administration officials, the Mondale appearance relates more to his friendship with Burton Joseph than to the nuances of foreign policy.