A Senate filibuster threat left presidential nominees for three senior foreign policy posts dangling in suspense yesterday after a token test of strength on the Senate floor.

Sens. Jesse Helms (R-N.C.), Orrin G. Hatch (R-Utah) and fellow conservatives easily blocked confirmation of the controversial nominations of Robert T. Grey Jr. as deputy director of the Arms Control and Disarmament Agency and Richard R. Burt as assistant secretary of state for European affairs.

In retaliation, Senate liberals -- through Joseph R. Biden Jr. (D-Del.) and with the backing of Edward M. Kennedy (D-Mass.) -- continued to block confirmation of a former Helms aide, Richard T. McCormack, as assistant secretary of state for economic affairs.

Nevertheless, Helms and fellow conservatives, who are demanding a tougher anti-Soviet policy by the Reagan administration -- with demonstrable evidence that they are an influential force in shaping U.S. foreign policy -- appeared to have won a victory.

The administration yesterday was unofficially reported to be prepared to sacrifice Grey to salvage the nomination of Burt, now in Europe with Secretary of State George P. Shultz. ACDA officials expressed astonishment and disbelief over that report.

Senate sources said Grey's abandonment by the administration could bring the resignation of ACDA director Eugene V. Rostow.

Rostow last month arranged for the transfer of one senior aide, Norman Terrell, to NASA in an attempt to placate the Helms faction.

Helms told Majority Leader Howard H. Baker Jr. (R-Tenn.) on the Senate floor yesterday that the administration is engaged in an "exercise in futility" in trying to have Grey confirmed. The Grey nomination, Helms said, "may very well be withdrawn by the White House later," along with that of "another" nominee.

A senior White House official later said "a decision has been made to withdraw Grey" in a manner still unresolved. ACDA officials said their information was to the contrary.

When White House spokesman Larry Speakes was asked for an official position on Grey's fate, he replied: "We have nothing to say on it."

In marked contrast, Speakes said that Burt "enjoys the full backing of the president and the secretary of state, and we urge his support and we are convinced of his loyalty to the administration."

At the outset of yesterday's maneuvering, Helms said he had "eight to 10 hours of material" to discuss on Grey, with Sens. Charles E. Grassley (R-Iowa), Steven D. Symms (R-Idaho), Roger W. Jepsen (R-Iowa) and Jeremiah Denton (R-Ala.) waiting in the wings.

"That is not a threat," Helms said drily, "just a friendly signal that I send to the majority leader." Baker responded equally drily that "this comes as no surprise to me," but said he wanted to confer with President Reagan.

Faced with a pile-up of legislation threatened by a filibuster, Baker said he will leave the Grey nomination in abeyance and see if progress is possible on other nominations.

There were rarely more than three or four senators present during the subsequent desultory debates.

Sen. Malcolm Wallop (R-Wyo.), speaking for himself and Senate Intelligence Committee Chairman Barry Goldwater (R-Ariz.), led the attack on Burt, saying that as a New York Times reporter in 1979, Burt grievously endangered national security with disclosures about the U.S. satellite reconnaissance system.

Sen. Charles McC. Mathias Jr. (R-Md.), in Burt's defense, said the charges involving Burt's reporting were weighed by the Senate Foreign Relations Committee in supporting his nomination.