The United States yesterday expressed "concern" about the takeover of the U.S. Embassy in Tehran, but administration officials refused to comment on the demands of the Iranian miltiants that the deposed shah be extradited to Iran.

The takeover underscored the increasingly nagging problem that the presence of Shah Mohammad Reza Phalavi in the United States has become. He currently is undergoing treatment for cancer at a New York Hosipital.

At least two recent bomb threats against a U.S. airline have been link-to demands for the shah's extradition, and Iranian demonstrators protesting his presence yesterday chained themselves to the crown of the Statue of Liberty in New York.

In addition, the issue shows signs of giving political ammunition to domestic opponents of President Carter. Republican presidential candidate John Connally yesterday blamed the embassy takeover on a policy of "appeasement" by the administration.

The Shah's presence also has further damaged U.s.-Iranian relations, which the administration considered to be slowly improving.

In response to the embassy takeover, the State Department formed an interagency "task force" headed by Assistant Secretary of State Harold Saunders and including representatives of the Defense Department and the National Security Council. But State Department officials sought to play down the incident publicy.

In statement, the department said the Iranian government had given assurances that it would try to resolve the problem.

The officials also said they did not consider the American held at the embassy to be "hostages," although the department acknowledged that the portestors "are not allowing them to leave." The officials estimated that 40 to 50 Americans are being held.

A State Department spokeswoman desbribed the takeover as a "peaceful demonstration" and said the Americans were "not being held at gunpoint to the best of our knowledge."

There were conflicting reports from Tehran on whether the demonstrators were armed. Some reportedly carried clubs.

The State Department statement on the embassy takeover said the U.S. charge d'affaires in Tehran, Bruce laingen, who was not in the mission at the time, had contracted Iranian Foreign Minister Ibrahim Yazdi about the incident.

"Through Laingen we have registered our concern with the Iranian authorities about this threat to American personnel and property," the statement said. "The government of Iran has given assurances that our people being held are safe and well. The charge has been given assurances by the Iranian government that it will do its best to resolve the matter satisfactorily. We appreciate the efforts of the Iranian government."

However, a later statement by the Iranian Foreign Ministry appeared to contradict the reported assurances and tacitly support the takeover. The statement said, "Today's move by a group of our compatriots is a natural reaction to the U.S. government's indifference to the hurt feelings of the Iranian people about the presence of the deposed shah, who is in the United States under the pretext of illness."

The State Department task force has been in contact with Laingen, but has been unable to get through directly to the Americans being held at the embassy, officials said. They confirmed that a contingent of 14 U.s. Marines guarding the embassy had fired tear gas in an effort to repel the Iranian demonstrators, but said no one was injured. It was not immediately clear how many Marines were being held.

Asked about the demonstrators' claim to have confiscated classified embassy files, a State Department spokeswoman said, "We understand that no sensitive material has been compromised."

The spokeswoman reaffirmed that the 60-year-old shah was admitted to the United States "on humanitarian grounds" to undergo medical treatment and that he is expected to leave the country afterward.

However, visitors who met the shah's family in New York last week said they came away with the clear understanding that the shah plans to stay in the United States "indefinitely" and expects to be allowed to do so by American authorities. The visitors said the family was upset with President Carter, complaining that the ailing monarch, who hosted Carter in Tehran on New York's Eve 1977, had not even received a get-well card from the president.

Former secretary of State Henry Kissinger has been active in trying to obtain U.S. permission for ths shah to remain in this country. Informed sources said the Carter administration told Kissinger that the possibility of Americans in Iran being held hostage in exchange for the shah was among the reasons that the government did not want him to take up residence here.

In criticizing the Carter administration's handling of the embassy takeover in Tehran, Connally said, "If appeasement were an art form, this administration would be the Rembrandt of out time."

Shortly after the shah arrived in New York Oct. 22, surgeons removed his gall bladder and scheduled chemotherapy treatments for lymphatic cancer, which a spokesman said the shah has had for six years. Iranian demonstrators have gathered frequently outside his East Side hospital, shouting slogans such as, "A peaceful death is too good for the shah."

In yesterday's demonstration, in New York, seven persons identifying themselves as Iranian students look over the Statue of Liberty for nearly four hours before surrendering to National Park Service police. They were being held for questioning.

The demonstrators had displayed a 20-foot banner reading, The shah must be tried and punished."