A pledge by Kuwait to give "early release" to a handful of Shiite Moslem prisoners persuaded airline hijackers last week to end their 15-day siege in Algiers and free 31 remaining passengers, U.S. officials said Friday.

However, the five or six prisoners, among 17 held in Kuwait for bomb attacks on the U.S. and French embassies in 1981, have not been released, the officials told The Associated Press on condition of anonymity.They said the gunmen, who had been promised safe passage, remain in Algeria contrary to what the Algerian ambassador to Washington said earlier this week.

According to this account of the deal, Algerian intermediaries faithfully conveyed Kuwait's promise to the hijackers. But the officials said Kuwait, which has a firm policy of not yielding to terrorism, may not have had any intention of letting the prisoners go in the first place.

"They have stood so fast for so long, they probably had no intention of letting them go early," one of the officials said.

The five-year prison terms of three of the 17 Shiite Moslems are due to expire at the end of the year.

During the long siege, the United States repeatedly urged Kuwait publicly and privately not to yield to the hijackers. But the Reagan administration was not aware of the terms.