WASHINGTON (AP) _ The State Department says it has no information on a report that the Shiite captors of six Americans kidnapped in Lebanon may be willing to drastically scale down their demands for the hostages' release.

As the price for the Americans' freedom, the kidnappers have insisted on the release of 17 terrorists imprisoned in Kuwait. But a report Tuesday indicated the captors may demand freedom for only two of the Kuwaiti prisoners.

The Washington Post, which reported the compromise proposal in its Tuesday editions, said the two are related to ''the big and religiously important Mussavi family of Lebanon.''

State Department spokesman Peter Martinez said the administration has received no such proposal and does not negotiate with terrorists in any case.

''We will not give in to terrorist demands, nor will we ask third parties to do so,'' Martinez said.

Peggy Say, sister of one of the kidnapped Americans, Associated Press chief Middle East correspondent Terry Anderson, said the hostage families were aware that two or three of the Shiites imprisoned in Kuwait were particularly important because of family ties to some of the kidnappers.

She said she does not recall hostage relatives suggesting the Americans be swapped for these two or three. But, she said, the hostage families have encouraged the administration to find out whether there is a lesser number than 17 that the Lebanese captors would settle for.

''The families have always said, find out what the bottom line is,'' she said in a telephone interview.

Besides Anderson, the Americans held captive are William Buckley, a U.S. Embassy political officer; Peter Kilburn, librarian with the American University in Beirut; the Rev. Lawrence Martin Jenco of Catholic Relief Services; Donald Jacobsen, administrator of American University Hospital; and Dr. Thomas Sutherland, dean of the school of agriculture at the American University.

Just six days ago, the Rev. Benjamin Weir, who was released after being held in Lebanon for 16 months, indicated his captors were standing by their demand that all 17 prisoners in Kuwait be freed in exchange for the Americans.

If there was no response soon, Weir said his captors told him, they were ready to kidnap more Americans and possibly execute the hostages.

Martinez said the United States was engaged in a ''regular dialogue'' with Kuwait on the general subject of terrorism but he gave no details. The 17 prisoners in Kuwait are said to have engaged in terrorist activities, including an attack on the U.S. Embassy there.

Kuwait, like the Reagan administration, has said it will not negotiate the release of the prisoners. On Tuesday, Kuwaiti Ambassador Sheikh Saud Nasir Al- Sabah said through an aide that he would not comment on the Post report.

Congressional sources, speaking only on condition of anonymity, said Tuesday that details of the reported Shiite compromise were given to the newspaper by Algerian Ambassador Mohamed Sahnoun, whose government has playing intermediary in the hostage situation for several months. Sahnoun did not return calls for comment Tuesday.

Meanwhile, U.S. officials who also insisted on anonymity said the U.S. Ambassador to the United Nations, Vernon A. Walters, made a secret trip to Syria last week for consultations with Syrian President Hafez Assad on the hostage issue.

The ambassador's spokeswoman, Irene Payne, said she was unable to comment beyond Walters' explanation last week that he was out of the country on a mission for the government.

Syria is believed to have influence over the Shiite group that has carried out the kidnappings. A spokesman at the Syrian Embassy, Mohamed Adib Khani, said he was not familiar with the proposal outlined in the Post.