The congressmen who headed an investigation of Chinese espionage in the United States yesterday criticized the Clinton administration for keeping a too-tight seal on their report.

Lawmakers have been struggling to declassify a report on Chinese thefts of U.S. nuclear secrets and recently extended the original March 31 deadline until the end of this month.

"Originally, I didn't think we'd use up even that much time. It now appears that we will do so," Rep. Christopher Cox, chairman of the Select Committee on Technology Transfers to China, said on "Fox News Sunday." The California Republican said some of the delay has been the fault of administration officials making unwarranted objections to releasing certain information.

Rep. Norm Dicks of Washington, ranking Democrat on the committee, who also appeared on Fox, called the spying by the Chinese the "most serious [intelligence] failures that I can recall except for the [Aldrich] Ames case."

He noted that the panel agreed unanimously that the report, completed in early January, should be made public. "You know we want to get this thing out as quickly as possible," Mr. Dicks said. But, unlike Mr. Cox, he did not suggest the administration is purposely trying to slow the release process down.

Mr. Cox said that declassification has been a tedious process, and that negotiations are being carried out "word by word, sentence by sentence, paragraph by paragraph."

"When there is an administration objection [to releasing something in the report] based on source or method of intelligence gathering, we have to walk back that claim and check out who is the source, what needs to be protected, and find if there isn't a way to write around it," the chairman said.

He said the committee understands those objections but not some others that have been put forth recently by the Department of Energy, which runs the nuclear weapons labs, where spying has gone on.

"Recently we've found that even though we reached agreement with the CIA or the FBI, the Department of Energy will have an objection, not based on sources or methods, but based on some other ground," Mr. Cox said.

He argued that "those kinds of objections not based on sources and methods are not proper," if declassification of the report is the "legitimate aim here."

"We're frankly trying to turn them around on that," the California Republican said.

Despite his dismay at the delay in releasing the report, Mr. Cox said, "I intend, and I think Norm does as well, that we get this out so you all can read it, so that Congress can read it, not just in classified sessions. And act on it before the end of the month."

The congressmen declined to discuss what's in the report, pending declassification. But Mr. Cox said there's more in it than what has been disclosed in the media. "The pattern [of espionage] is broader still ... in fact, the pattern extends back several decades and continues almost certainly until this very day."