A medical examination shows that two American soldiers were "murdered in cold blood" by leftist rebels after their helicopter was shot down, the U.S. ambassador said Saturday.

"I believe they were executed," Ambassador William Walker told a news conference at which he discussed the examination of the bodies of the three men who were aboard a U.S. army helicopter shot down Wednesday.Dr. Glenn N. Wagner, an army medical examiner brought to this country to aid an autopsy on the victims, used the term "homicide" to describe the deaths.

The third man died of injuries suffered in the crash of the helicopter, officials say.

The finding supported earlier claims by State Department and Pentagon officials that the men had been executed by rebels of the Farabundo Marti National Liberation Front, which has waged an 11-year war against the U.S.-backed Salvadoran government.

It also bolsters efforts of this country's right-wing government to free $42.5 million in U.S. military aid frozen last year by Congress because of concern over human rights abuses.

President Bush is expected to decide whether to restore the aid - an action he can take if the rebels act to prolong the war or threaten to overthrow the government.

The rebels have denied the allegations of murder and called for an independent investigation. The rebels said the soldiers were gravely wounded by the gunfire that brought down their UH-1H Huey helicopter and by the crash itself, and died minutes later of their wounds.

Lt. Col. David H. Pickett and Pvt. 1st Class Earnest G. Dawson were slain with gunfire from two assault rifles and a handgun, the U.S. report said.

The report said that only Chief Warrant Officer Daniel S. Scott died as a result of the helicopter crash itself.