The Reagan administration, which held its tongue until two American survivors had left Tehran, cast a large measure of blame yesterday on Iran for the handling of the recent hijacking episode and charged that Iranian actions encouraged "extreme behavior" by the killers of two American hostages.

Identical statements by White House and State Department spokesmen, issued shortly after businessman John Costa and U.S. Agency for International Development official Charles Kapar departed on the first leg of their trip home, said Iran's actions "raise profound and disturbing questions, to which we are seeking answers."

"Two passengers were murdered by the hijackers, more were tortured and many were brutalized for an extended period of time without any effective measures being taken by the government of Iran.

"Granting selective media access, broadcasting statements and screams of tortured passengers, permitting photographers aboard the aircraft, clearly encouraged extreme behavior by the hijackers," the U.S. statement said.

The bodies of AID officials Charles F. Hegna and William Stanford, who were killed by the hijackers of the Kuwaiti Airlines jet, are scheduled to be received with full honors at Andrews Air Force Base this morning in a ceremony that may provide another occasion for the expression of U.S. ire. Vice President Bush is to lead the government delegation to the ceremony.

AID Administrator M. Peter McPherson, in a statement officially confirming the two deaths after positive identification of their bodies, condemned "the heinous murder of two American public servants" and "the physical and psychological torture and relentless death threats" against all the U.S. hostages on the airliner.

President Reagan, commenting briefly to reporters while posing for pictures at the White House with visiting Niger President Seyni Kountche, said that "the Iranians could have done a better job" of handling the six-day hijacking even if they were not in collusion with the hijackers.

Reagan and other officials, including Secretary of State George P. Shultz, declined to express a firm judgment about possible Iranian complicity with the hijackers until the surviving Americans are interviewed and information is gathered from a variety of other sources.

The official U.S. statement, however, left open the possibility that Iran was partly responsible for the deaths of the two Americans. Saying that Iran has shown that it can act "rapidly and effectively to end hijackings when it wishes," the statement noted that this time, Iran "did otherwise" with innocent American, Kuwaiti and other lives at stake.

"Two U.S. government employes were murdered. We will probably never know what would have happened had the Iranian government acted more firmly," the statement said.

The White House and State Department spokesmen also repeated the previous call on Iran to place the hijackers on trial for their actions or extradite them to another country for trial. This is Iran's "very clear obligation" under the international convention against hijacking, which that country signed, according to the statement.

Iran's failure to try or extradite earlier hijackers "reinforced the impression that Iran is sympathetic to and provides a safe haven for hijackers," the statement said.

The future U.S. "attitude and actions" toward Iran will be affected by its actions in the aftermath of the hijacking, which will be "closely" watched by the administration, according to the declaration.

Shultz, speaking to reporters aboard his plane en route to England and a meeting of the Atlantic alliance in Belgium, said that, "It was a long time that that airplane was on the Tarmac [at Tehran airport] before definitive action was taken."

Washington Post staff writer John M. Goshko reported that Shultz reiterated his backing for "active defense" including military action to combat terrorism. "I think strong action, if we can identify it precisely and execute it successfully, will command broad support" among the public, Shultz said.

U.S. officials said there is little likelihood of retaliatory action at the present time against those thought to be associated with the hijacking of the Kuwaiti jet and the killing of the two Americans.

"As far as we're concerned, we haven't talked about retaliation in terms of revenge," said Shultz. "Our notion is there may be times when prevention takes on an aspect of retaliation. The object is to defend yourself but actively. We are not talking of revenge. We are talking about defending yourself."

Shultz, who has been the most outspoken advocate of using military force against terrorism, was pressed by reporters about his differences on the issue with Secretary of Defense Caspar W. Weinberger. In a Nov. 28 speech Weinberger said that before U.S. combat forces are committed abroad "there must be some reasonable assurance we will have the support of the American people and their elected representatives in Congress."

Shultz said, "I think it's been a healthy discussion and somewhat parallel. I totally agree that we need broad support. But you don't stop and take a public opinion poll before you act."