The White House declined yesterday to say whether an attack in Nicaragua Monday by antigovernment rebels against a convoy escorting foreign journalists showed that the insurgents had violated the administration's stated reasons for providing them with aid.

White House spokesman Larry Speakes was asked how the administration accounted for the rebels' apparent use of American weapons, which U.S. officials say have been provided to block Nicaraguan supply routes to leftist guerrillas in El Salvador. "I do not know the circumstances," Speakes said.

Asked whether the use of U.S. weapons in this case would be a violation of Washington's stated purpose, Speakes said, "The president has stated that the purpose is to interdict the supply lines going into El Salvador. That's the latest I have on it."

"We're not looking into a reporter's news story that's on the front page of The Washington Post," he said. "What I'm indicating to you is that just because a story appears in the local newspaper, we don't go running down there."

The story, by Post Foreign Editor Karen De-Young, described the ambush by about 100 Ni-caraguan rebels of a military convoy escorting De-Young and 11 other foreign journalists out of the town of Jalapa near the Honduran border. Five government soldiers were killed and six were wounded.