The Senate Foreign Relations Committee told the Carter administration yesterday that "the time has come" to begin formal consultations under the War Powers Act about possible U.S. military action against Iran.

In a letter to Secretary of State Cyrus R. Vance, Chairman Frank Church (D-Idaho) and ranking minority member Jacob Javits (R-N.Y.) said the advance consultation provisions of the 1973 law are intended to ensure a role for Congress before any decision regarding U.S. military action has been made.

The law, which was passed over President Nixon's veto as part of the legislative reaction to the Vietnam war, calls for presidential consultations with Congress "before introducing U.S. armed forces into hostilities or into situations where imminent involvment in hostilities is clearly indicated by the circumstances."

The legislative history of the law, according to Church and Javits, makes it clear that "advance consultations" are to be conducted with the congressional committees having jurisdiction over foreign policy. "Accordingly, Mr. Secretary, we hereby request that you inform this committee at an early date when consulations can begin," the letter to Vance said.

The demand for consultations was prompted, the senators said, by "the grave international crisis" in the Persian Gulf and President Carter's public statements about the possibility of U.S. military action in the hostage crisis.

Carter had repeatedly hinted in recent days that he is weighing a naval blockade or mining of Iran's ports if economic and political pressures do not bring about the release of the U.S. hostages from Iranian captivity in the next month or two.

In a separate statement, Sen. Claiborne Pell (D-R.I.), who ranks next to Church on the majority side of the committee, declared his opposition to "the unilateral use of military force" at this time. Pell said that "once military action is taken, I fear that the first action will be followed by another and then another . . . The lives of the very people that the military actions are designed to save will be jeopardized, and the Soviets may be tempted to intervene in order to 'save' Iran.

Senate Majority Leader Robert C. Byrd (D-W.Va.) said Wednesday that he has notified the White House in recent days that Congress must be fully consulted if military action is being contemplated. The formal letter from the Senate Foreign Relations Committee takes one step further the congressional insistence on a role in Carter's decisionmaking.

The uncertainty about Carter's intentions came under sharp attack from former secretary of state Henry A. Kissinger, who criticized "endless bureaucratic debates on the essential elements of our strategy in the middle of a crisis."

Speaking at a conference here on "Totalitarianism and Terrorism," Kissinger suggesed that the United States lacks strategy, I do not ask that all of it be spelled out publicly but have we spelled out to ourselves?" he asked.

"Gradual backing into [forceful action] with advertisements of insecurity" may be the worst of all choices, he said. If and when strong action is decided upon, "an implacability not affected by every gust of public opinion" is necessary, according to Kissinger. He added, "public opinion polls are not a reliable guide to action."

In an interview with a group of editors and broadcasters, released yesterday Carter said he would have preferred that the European allies take "stronger and more immediate action" in the Iran crisis. But he added, "I think the action, whatever it is, is more effective with the whole community being in favor of it. I hope that will have a sobering effect on them [the Iranians.]"

Sen. Henry M. Jackson (D-Wash.), in a speech last night, charged that Carter's "preoccupation" with the hostages has led him to underestimate "the danger of a divided and weakened Iran falling into the Kremlin's Lap" Jackson called on the administration to "stop thinking and talking" as if the Iranian nation -- rather than the Soviet Union -- is the major adversary.

"We cannot afford a foreign policy tuned to the vagaries of presidential primaries and presidential polls," Jackson said.

The State Department, through spokesman Thomas Reston, sought to downgrade Iran's moves toward an economic accord with Moscow. Reston said that despite reports of Tehran-Moscow negotiation, the United States has "no evidence" that the economic sanctions imposed by the western nations will result in a major increase in Iranian-Soviet trade.

"We don't believe Iran's true national interest would be served" by closer links with the Soviets, Reston said.