The Federal Bureau of Investigation this week took the unusual step of asking a number of news executives for any information "positive or negative" they might know about President Reagan's two Supreme Court nominees, William H. Rehnquist and Antonin Scalia.

Those contacted by the FBI, however, said that they knew little or nothing about the nominees personally or that they told bureau representatives any information they felt they could release to the FBI would be published first.

Rehnquist was nominated by President Reagan to be chief justice of the United States upon the retirement this summer of Warren E. Burger and Scalia was named to be an associate justice to replace Rehnquist. Both nominations are subject to Senate confirmation.

FBI agent Steve Raimey of the Washington Field Office said he had been asked by headquarters' officials to talk to Washington network television bureau chiefs and Washington Post Executive Editor Benjamin C. Bradlee about the nominees. He said it was his understanding that in the past major religious groups and other national organizations had been contacted for their opinions about those proposed for the judiciary.

NBC News reported Tuesday evening that an FBI agent said "the government wants to find out 'sooner rather than later' what the major news organizations might have on Rehnquist and Scalia."

"I don't think this is a clandestine thing," Raimey said. "We looked at it as an opportunity to have them voice their opinion."

"They called our Washington bureau chief, Jack Smith, and he talked to me about it," said David Buksbaum, CBS vice president for news coverage and operations. "We decided to tell them that anything we find out pro or con we are going to report. You can find out by watching the broadcast. Our feeling is that if we have anything to say, we're going to say it on the air."

Bradlee said that when he was first contacted to be interviewed, "I thought it was a practical joke" because he did not know Scalia and had only met Rehnquist.

Bradlee said he told FBI agents who went to his office yesterday that "I don't know anything about them, and I specifically refrained from commenting on their opinions and their reputations based on those opinions."

Robert McFarland, Washington bureau chief of NBC News, said that he had not yet spoken with the FBI agents but would talk to them because "I'll always talk to the FBI. But all I can say is that we don't have anything," he said.

ABC News Washington bureau chief George Watson said that when an FBI agent called him, he said, "I had nothing to say. I know nothing except what I read in the paper and saw on the broadcasts . . . . "

Raimey said that he had not been asked to call The New York Times or The Wall Street Journal; if those papers were contacted, it would be through the New York Field Office.