The State Department formally asked the Organization of American States on Wednesday to approve the expulsion of Nicaragua's ambassador to the United States who also serves as OAS ambassador.

Richard McCormack, the U.S. ambassador to the international body, delivered a note to Ambassador Eladio Knipping of the Dominican Republic, who is also president of the OAS permanent council."If you (are) in violation of your diplomatic status in the United States, Article 3 of the OAS Privileges and Immunity Agreement does not exempt you from expulsion," said Russell Wa-pensky, a State Department official.

Meanwhile, Richard Melton, the U.S. ambassador to Nicaragua who was expelled by the Sandinista government along with seven colleagues, said Wednesday he believes Nicaragua took the action in order to intimidate the opposition.

Melton told a White House news conference that the Sandinistas wanted to demonstrate to the opposition that "they are alone and isolated with nowhere to turn."

He noted that one of the functions of those expelled was to deal with opposition leaders. He flatly denied that the embassy was involved in organizing and financing the opposition.

On Capitol Hill, senators angered by Melton's expulsion and the shutting down of the newspaper La Prensa and the Catholic radio station prepared to introduce legislation condemning the Sandinista government and providing further economic and perhaps military assistance to the Contras.

"We are moving now because the Sandinista goons have been in the streets of Managua again . . . because the light of freedom has been nearly snuffed out again," said Senate Republican leader Bob Dole of Kansas.

House Speaker Jim Wright of Texas said a bipartisan group of lawmakers is drafting a House resolution that "will call upon the Nicaraguan government to re-open the organs of free expression and repeal the law that permits the response they made."

Members of the Senate Intelligence Committee attempted to hold a public hearing to question Melton on the reasons behind his expulsion but were blocked by an objection lodged by Sen. Christopher Dodd, D-Conn., an opponent of Contra aid.

Chairman David Boren, D-Okla., told reporters that he and other committee members had questioned Melton privately and found no indication that either he or any of his fellow diplomats were engaged in espionage or other acts that might have justified their expulsion.

Earlier, Nicaraguan Ambassador Carlos Tunnermann said he would consult with his government on whether to challenge the legality of the U.S. decision to order him out of the country.

Deputy Secretary of State John Whitehead said Wednesday on NBC-TV's "Today" that the United States has no plans to cut diplomatic ties with Managua. "It's important for us to maintain contact in some kind of relations even with government that we have very little respect for," Whitehead said.