The United States called on its allies yesterday to support President Carter's newly hardened line against Iran in order to head off a more dangerous situation if the hostage crisis remains unresolved.

Senior White House and State Department officials declined to give a list of the measures the United States is asking the European allies and Japan to take. They said that Washington is seeking "collective action" to impress Iran with the seriousness of the long-running hostage crisis, but that the allies are not expected to match each of the steps announced by Carter Monday.

The U.S. requests are to be amplified here today by Secretary of State Cyrus R. Vance, who has invited the ambassadors of some two dozen friendly countries to the State Department to solicit their cooperation.

In advance of this, U.S. diplomats have asked a number of friendly European contries and Japan to support Washington's effort by removing their ambassadors from Tehran or otherwise lowering their level of diplomatic contact, and by cutting back on their trade and economic ties with Iran, according to official sources here.

"We will be awaiting with interest their response in this matter," said White House press secretary Jody Powell in discussing the requests to the allies through diplomatic channels. "To the extent that they support us in these efforts, the crisis is more likely to be resolved without the necessity for additonal actions which could involve risks for all concerned."

State Department spokesman Hodding Carter said the Iranian situation would become "more dangerous" if it drags on.

Neither spokesman, would spell out the risks and dangers, which are believed to include U.S. military action that could jeopardize the continued flow of Iranian oil to our allies and other petroleum-importing nations.

Officials said it is to early to tell how fully and how openly the allies will react to the new American requests. State Department officials have credited the allies with quiet but important cooperation with U.S. economic strictures against Iran in recent months.

According to State Department spokesman Carter, Washington made no effort to line up joint announcements or joint action involving the allies in advance of the presidential announcements Monday. But he stressed that the effectiveness of the new U.S. measures will be heightened if the allies cooperate to heighten the sense and reality of Iranian isolation from the rest of the world as long as the American diplomats are held hostage.

U.S. officials said they were not surprised by the bitterly hostile tone of the first Iranian responses to the presidential announcements. In their view, the authorities in Tehran are seeking to intensify a spirit of national unity in the face of growing external pressures.

Washington sources noted that, despite the harsh rhetoric, there was no immediate sign of actions regarding the hostages that would aggravate the heightened tension with the United States.

In addition to the hostagtes crisis, a newly intensified conflict with its neighbor and traditional enemy, Iraq, confronts Iran. The current political and military clashes between the two Perisan Gulf states were seen here as the most serious of recent months, but sources said there is no clear indication whether Iran-Iraq relations will continue to spiral downward toward large-scale confrontations.

In view of the unsettled Iranian domestic climate, administration officials were reluctant even to guess what effect Iran-Iraq confrontations might have on the problem of the U.S. hostages.

There was no sign of a change in the deployment or alert status off U.S. naval forces on station near the Persian Gulf, despite the Iran-Iraq tension and the shift in White House policy toward greater pressure on Iran in the hostage crisis.

Sen. George McGovern (D.S.D.) in a statement released in his home town, said the Carter administration should begin planning now for the possibility that military action will be necessary to break the hostage stalemate. McGovern said the plans should include "imposition of a blockade and even selective American air strikes against Iranian installations, if these become necessary to resolve this unprecedented and outrageous political kidnaping."

The most urgent and immediate business for many foreign policy officials here yesterday was the departure arrangements for Iranian diplomatic personnel who were given until last midnight to leave the United States. As the Iranians scrambled to pack up and depart, several expressed dismay and anger. The acting Iranian consul in Houston, Hassan Taherian, said in a statement that he and his associates "express our profound happiness for leaving the United States and returning to our beloved coountry."