U.S. Ambassador to Moscow Malcolm Toon tonight declared he is "reasonably confident" his doubts about the verifiability of the new Soviet-American strategic arms limitation treaty soon "can be worked out in a satisfactory way," ensuring his public support of the pact.

At an impromtu press conference during a reception at the ambassador's official residence, Spaso House, Toon said he believes the SALT II treaty "is an important stabilizing element in U.S-Soviet relations, contitutes a valuable contribution to arms control and does not in any way weaken the security position of the United States."

Thursday, American sources were reported to have learned at the Vienna summit that Toon was hinting privately he had new, previously undisclosed reservations about the agreement, which was signed Monday by President Carter and Soviet leader Leonid Brezhnev. The ambassador's doubts were said to center on the loss of U.S. eavesdropping stations in Iran, for which no adequate replacemant has yet been reported.

Tonight, Toon said he "regretted" press reports which he said "have left the erroneous impression that I have changed my mind about the SALT II treaty. This is not true." Toon has supported the treaty.

However, he did not deny he had expressed reservations to Secretary of State Cyrus Vance's staff about the treaty the president had signed.

"Like other responsible U.S. govenment officials, I feel strongly that no agreement with the Soviet Union, or for that matter with any other major power, should rest on trust.

"It must be verifiable. It is for this reason that I intend to satisfy myself that the treaty is verifiable when I return to Washington in July."

Toon's possible defection from support would be a blow to the administration as it begins the fight for Senate ratification of the treaty. Senate opposition has coalesced aroung the issue of verification of Soviet tests of new missile types.

He said he thought the chances of having his doubts resolved favorably were "pretty good." Pressed to say what he would do if they are not, he said, "I'll face that problem if it arises."

Toon helped negotiate the treaty with the Soviets, plating a major role in the first two years of the Carter administration's talks with the Kremlin.

His influence on the talks has waned in recent months as the exchanges between Vance and Soviet Ambassador to Washington Anatoliy Dobrynin became the centerpiece in the negotiations.

Toon declined tonight to say more, and did not explain why, since the Iranian spy bases were lost months ago, his reservations about this are only now being voiced. One source suggested that it was because the ambassador during the summit had had time to concentrate on the problem in a way he could not in Moscow.

Toon had no comment on the reported selection of retired IBM chairman Thomas J. Watson Jr. as his successor. He has made it clear almost since arriving in Moscow in December 1976 that he believes a career diplomat must be the American envoy here. Watson has no experience as a diplomat. Toon is scheduled to retire later this year.

Toon's present position is unique for a diplomat, withholding full fledged support for a treaty signed by the president with the leader of the country to which Toon is accredited. But his career has been marked by a tough-talking independence that has sometimes brought him public attention and which the Soviets themselves have made clear they do not especially like. In 1977, the Soviets barred him from nationwide television when they apparently objected to his remarks supporting the importance of individual freedoms. And the Soviets have taken exception to statements Toon has made in the United States about this country's policies on a variety of matters.