President Bush told Congress Tuesday that he has decided to authorize release of an additional $42.5 million in military aid to El Salvador because leftist rebels fighting the U.S.-backed government have violated conditions set by Congress last fall when the aid was withheld.

The money will not be released for another 60 days, according to White House press secretary Marlin Fitzwater, to see if the rebels take a "serious and constructive approach" to U.N.-supervised peace talks so a political settlement and cease-fire can be reached within that time. If the cease-fire is agreed to, Fitzwater said, then the additional money will not be released.

The administration said it had determined that the money -- half of the military aid this year to El Salvador -- could be released because the rebels violated the congressional prohibitions against attacking civilian targets and receiving "significant shipments" of arms from outside the country.

It had been widely assumed that the administration would authorize release of the withheld funds, especially after rebels earlier this month apparently shot to death two U.S. servicemen who were injured when their helicopter was downed by rebel gunfire.

Bush, in his report to Congress, also said he was "not satisfied with the cooperation of the {Salvadoran} armed forces in the investigation" into the 1989 murders of six Jesuit priests, according to a State Department official. The official, who declined to be identified, said that during the 60-day waiting period the administration would monitor the progress of the prosecution of Salvadoran troops believed responsible for those murders and that progress in that case would be a factor in determining whether the withheld aid would be released.