Efforts to obtain the safe release of 60 to 65 American hostages at the U.S. embassy in Tehran fell victim to confusion amid new fears for the prisoner's safety last night after Iranian leaders refused to allow two special American envoys into the country.

The new setback came against a background of political chaos in Iran and deep uncertainty in international oil markets that sent spot oil prices soaring and touched off fears of shortages producing new gasoline lines in the United States.

The two emissaries, former attorney general Ramsey Clark and Senate staff member William G. Miller, left Washington secretly early yesterday with a message from President Carter of Iran's revolutionary leader, the Ayatollah Rubollah Khomeini.

But their journey ground to at least a temporary halt in Istanbul after Khomeini, overturning an earlier decision by his revolutionary government, said that neither he nor other responsible Iranian officials would meet the two Americans.

That left the two marking time in Istanbul while the State Department sought to learn whether they eventually will be able to proceed to Iran. But, as of last night, U.S. officials were unable to predict the future status of the mission.

At the same time, fears for the safety of the hostages increased in Washington because of reports that their Iranian captors, who are demanding the extradition of deposed Shah Mohannad Reza Pahlavi, were subjecting them to psychological abuse.

On the oil front, despite assurances by U.S. officials that the spigot had been turned on again after a brief shutdown Tuesday, Energy Secretary Charles Duncan Jr. warned that the situation was unpredictable. He and other U.S. officials said they did not know if the interruption was a result of a local dispute or a signal of a possible boycott against the United States.