Secretary of State Cyrus R. Vance met Soviet Ambassador Anatoliy F. Dobrynin last night to discuss completion of a new strategic arms limitation treaty (SALT) as the pace of Washington deliberations on the issue quickened notably.

Officials said in advance of the meeting that they expected the latest positions from Moscow to be helpful in establishing the timetable for a final agreement. Vance, in private discussions on Capitol Hill earlier this week, reportedly described an accord on the major outstanding points as imminent.

After the meeting, there was no statement from either side.

Vance would not predict when the deal might be sealed and a summit meeting of President Carter and Soviet President Leonid Brezhnev announced for the ceremonial signing and exchange of formalities on the Soviet "Backfire" bomber and perhaps a few other issues. Administration officials concerned with SALT have been involved in an unusually heavy round of meetings to prepare treaty language and explanations to legislators and the public of what has been decided.

The sudden postponement of the planned visit to Moscow this week of French President Valery Giscard d'Estaing because of the illness of Brezhnev raised speculation and some alarm that the 72-year-old Soviet leader might be too sick to attend a summit meeting with Carter or might even be fading from the scene. Brezhnev has been in declining health for several years.

These apprehensions were eased a bit yesterday when U.S. officials learned that the Soviets had proposed a new date several weeks hence for Brezhnev to meet the French leader. No date was announced, because of French scheduling complications, according to this report.

In another in the new round of SALT discussions, Carter met for breakfast Wednesday at the White House with the Joint Chiefs of Staff to receive what may be final military advice on the treaty.

The uniformed chiefs, who have been engaged in intensive deliberations of their own on the subject, are officially reserving judgment. But a Pentagon official said the chiefs view the treaty as presently planned to be "marginally better than no agreement," providing spending programs are approved to modernize the U.S. strategic nuclear force while SALT II is in effect.

The last two major negotiating questions remaining to be decided, according to administration sources, involve details of the definition of "new missiles," which are restricted under the treaty, and further Soviet assurances regarding the encoding of missile test data, or telemetry. The Soviet practice of encoding some of this data is to be limited under an agreed treaty provision, but detailed interpretations are still being negotiated.

The United States is prepared to make marginal compromises about the definition of new missiles, but is holding out for clear and strong Soviet assurances about encoded telemetry, officials said.

A SALT-related problem under intensive discussion within the administration and on Capitol Hill is the loss of certain intelligence data on Soviet missile programs as a result of the closing of the former U.S. surveilance bases in Iran. Administration offficials said that the information needed to monitor Soviet programs and compliance with the SALT II treaty can be obtained by other means, however.

Sen. John Glenn (D-Ohio), who has taken a special interest in SALT verification said that despite much discussion of the subject no formal proposal for substitute surveillance systems has been presented to lawmakers. Glenn said it would be useless to complete the treaty until its verification can be assured.