House Speaker Jim Wright defended himself Thursday against charges that he improperly disclosed a covert CIA operation in Nicaragua as Republican leaders formally asked for an investigation of his actions.

"I haven't revealed anything that was committed to me as secret or classified," Wright told a reporter. "I am not a member of the (House) Intelligence Committee. I have not been present at the secret, classified briefings. I have simply said what is generally known and what is true."But Wright, D-Texas, declined to specifically say how he had learned of the covert operation in Nicaragua, or whether he had been told of it informally by an Intelligence Committee member.

Wright on Tuesday said he had received "clear testimony" from the CIA that the agency had fomented opposition demonstrations in Nicaragua to provoke the leftist Sandinista government and sabotage peace talks. He told a reporter later that CIA officials had made the admission under congressional questioning.

He repeated the assertion to reporters today, noting that the Reagan administration had not disputed it.

"In late August of last year I became aware that elements of the U.S. government were seeking to ... foment disturbances with a view to seeing if they could provoke" the Sandinistas into a crackdown that would derail peace talks, Wright said.

"That seems to me just intolerably two-faced," he said. Wright added that he had been given "indirect assurance" that the practice has now been halted.

To bolster his case that the CIA activity already was well known, Wright distributed a list of news stories that document agency activity in Nicaragua. The list included past CIA actions such as mining Nicaraguan harbors, secretly resupplying the Contra rebels and supporting opposition groups, but contained no specific mention of covert efforts at fomenting civil unrest.

Meanwhile, House Minority Leader Bob Michel, R-Ill., and Rep. Dick Cheney, R-Wyo., chairman of the House Republican Conference, asked for an investigation of Wright's actions in letters late Wednesday to the House ethics and intelligence committees.

"Because of the possibility such a disclosure (of classified information) may have occurred, we are writing to ask your committee to promptly and thoroughly investigate the circumstances surrounding these events and to recommend appropriate action to the House of Representatives," Michel and Cheney said in a letter to ethics committee chairman Julian Dixon, D-Calif.