The Senate Judiciary Committee has scheduled an unusual closed hearing on the nomination of CIA general counsel Stanley Sporkin to a federal judgeship, saying it must examine allegations involving sensitive intelligence information.

Sporkin's nomination to the U.S. District Court for the District of Columbia has been held up for 16 months, largely because of opposition from conservative senators including Sen. Jeremiah Denton (R-Ala.).

Sporkin is disliked by some conservatives because of his aggressive tenure as enforcement chief of the Securities and Exchange Commission before he joined the CIA in 1981.

CIA Director William J. Casey has offered to testify at the closed Senate hearing scheduled for Oct. 21, and other CIA officials may also be asked to testify, according to sources.

The hearing will examine allegations that Sporkin improperly intervened in a Justice Department investigation of a leak of classified CIA information to a Middle East publication, the sources said.

They said it will question whether Sporkin alerted a former CIA official to the leak investigation before advising him to hire a lawyer. The official resigned last year after the probe began.

Sporkin called the allegation "nonsense" yesterday, saying: "There's no question at all, no evidence at all about my notifying someone of an investigation."

Sporkin said he had not previously known the CIA official. The leak investigation was already under way when he learned of it and "went and helped him get a lawyer," Sporkin said. He said this was part of his job as the agency's counsel.

Sporkin said it was "very bothersome" that his nomination has been delayed while opponents "try to impeach someone's integrity . . . . It's important that we have a hearing. I've got [to protect] my reputation and my integrity . . . . "

Some committee Democrats have urged Chairman Strom Thurmond (R-S.C.) to open the hearing, as is usual in judicial confirmations. But Mark Goodin, a spokesman for Thurmond, said, "The chairman intends to have a closed hearing because of the number of classified documents involved . . . and the sensitivity of the documents."

Sporkin may also be questioned about his 1983 role in ordering two CIA agents to withdraw their money from a Honolulu investment firm that collapsed amid fraud charges six months later.

Sporkin has said he knew nothing of the firm's financial problems but viewed the agents' investments as a conflict of interest because the firm had some ties to the CIA. Company founder Ronald R. Rewald is on trial for defrauding investors of $22 million.