Despite a new U.S. message last week, Iran still has not sent an "authorized" reply to American entreaties about talks on normalizing relations after an eight-year lapse, a Reagan administration official said Monday.

The message reiterated U.S. desires to discuss ties with Tehran and did not lay down conditions for a resumption of relations, broken in April 1980, said the official, who spoke on condition of anonymity.He said the United States would like to talk to the Iranians about the nine Americans held hostage in Lebanon, terrorism and ending the Persian Gulf war. He said, however, that the United States had not imposed conditions for talks.

Meanwhile, Iraq said it captured thousands of enemy troops in a series of sudden raids into Iran and promised Monday to end its invasion just as the two sides were preparing for peace talks.

Iraq's announcement, carried on government-run Baghdad radio, came after Iran claimed it attacked Iraqi forces in southern Iran Monday, forced them to retreat 25 miles and killed or wounded 1,500 Iraqis. The Iranian account could not be independently confirmed.

Iraq said it would withdraw from all Iranian territory within a day. On Sunday, Iraq reported its troops already had left Iran.

The new reports came as the warring nations' foreign ministers prepared to meet with U.N. Secretary-General Javier Perez de Cuellar for talks on a cease-fire.

Exactly one week ago and after a string of battlefield defeats, Iran abruptly changed its hardline stance and accepted a U.N. resolution for ending the 8-year-old war between the Persian Gulf neighbors.

Foreign Minister Ali Akbar Velayati of Iran, who was flying to New York Monday, said Iraq's wide-ranging attacks along the war front threaten a prospective cease-fire.

On Sunday, two senior U.S. officials said the administration deserves much of the credit for Iran's acceptance of a cease-fire in its long war with Iraq.

"This is a time, if not for bragging, at least it's been a time for all of us to be proud that our policy has been a success," said John Whitehead, deputy secretary of state.

Defense Secretary Frank C. Carlucci agreed and said a cease-fire means the year-old policy of escorting reflagged Kuwaiti tankers through the Persian Gulf will end "as soon as we judge it safe (and) prudent to do so."

But Carlucci, appearing on the NBC-TV program, "Meet the Press," refused to set a date for the reduction of Navy ships in the waterway. There are 27 U.S. warships there, compared with the five or six that patrolled the gulf before the convoys began.

Carlucci also said improved U.S.-Iranian relations could lead to the release of the nine Americans held hostage in Lebanon by Iranian-backed groups.

"We're obviously not going to discuss any quid pro quo, but if the Iranians want to talk to us about the hostage situation and how they're going to go about influencing their release, we'd be delighted to talk to them about it. I'm not in the slightest suggesting that there would be any deal for the hostages. That is contrary to our policy," he said.

Whitehead, asked on ABC's "This Week With David Brinkley" about the same reports, said, "I have no information (to indicate the reports are true)."

White House spokesman Marlin Fitzwater said Sunday the hostage situation is easy for Iran to resolve. "All they have to do is release them."

Fitzwater, speaking to reporters aboard Air Force One as President Reagan returned from California, said, "We are willing to talk to anybody, anyplace, but we are not willing to negotiate. We are not willing to pay ransom. There is no need."

On Sunday, a four-member U.N. team arrived in Iran to begin discussing a key technical elements of a truce: the trade of prisoners of war. A second U.N. team was scheduled to arrive soon in the Persian Gulf to work out other details of a cease-fire.

Interviewed Monday on ABC's "Good Morning America," Iranian and Iraqi diplomats charged each other's countries with violating the spirit of the prospective truce.

"At the last minute they want to capture some of our land when we have already removed the excuse for the Iraqis," said Mohammed Ja'afar Mahallati, Iran's ambassador to the United Nations. "Unfortunately it has been Iraq that has always sabotaged efforts of the secretary-general to implement (U.N. Resolution 598)."

Abdul Amir al-Anbari, Iraq's ambassador to the United States, criticized Iran for waiting a year to accept the U.N. resolution "and coupled with that, of course, all threats and calls for mobilization and asking the Iranian people to go to the front to continue the war against what they call the enemy."

"We are interested in lasting, comprehensive peace, not just a cease-fire to enable the Iranians to mobilize and wage another human offensive whenever they would like," he said.

Supreme Court Chief Justice Musavi Ardebili of Iran said Ayatollah Ruhollah Khomeini had "doubled his popularity" by accepting the cease-fire, Iran's official Islamic Republic News Agency reported Monday.

Tehran radio said Khomeini met with a group of visitors who chanted "Please God Keep Khomeini Alive" and "We Are All Your Soldiers, We Will Obey Your Orders."

The radio said Khomeini responded by waving his hand. He apparently did not speak.

According to International Red Cross figures, Iran has about 50,000 Iraqi POWs and Iraq held 13,000 Iranian soldiers before the latest raid. Iraq said Sunday that it had boosted its bargaining position by seizing 8,636 additional enemy fighters.