In a July 6 opinion piece published in The New York Times, former ambassador Joseph Wilson refuted Bush administration claims that Iraq tried to purchase uranium from Niger, writing in the article that US intelligence was "twisted to exaggerate the Iraqi threat."

In an interview with NBC television Tuesday, Wilson alleged that press leaks from the White House have attempted to malign him in an effort to dissuade others from speaking out.

"What I'm most worried about, most concerned about is that it is probably intended to intimidate others, and keep them from stepping forward," Wilson said.

He said that what he considers "the most serious allegation" appears in US media reports asserting that his wife is a Central Intelligence Agency spy. Wilson said reporters he spoke to about the reports cite "senior administration" officials as their source.

"That basically means that somebody at the political level of the administration," said Wilson, a former acting US ambassador to Iraq and a former envoy to .

He would neither confirm nor deny whether his wife works for the CIA, but said officials in the George W. Bush administration might have violated the law if she is, in fact, a covert US intelligence operative and was exposed as such by US officials.

"It would be damaging not just to her career ... it would be her entire network that she may have established, any operations, any programs or projects she was working on" which would be compromised, he said.

"It's a breach of national security," said Wilson. "My understanding is it may, in fact, be a violation of American law," he told NBC.

"I fully expect the appropriate authorities will look into it, as well they should.

A senior US senator who has been one of the leading critics of the Bush administration on the question of its prewar Iraq intelligence, called on the floor of the US Senate for an investigation into the matter by the Senate Intelligence Committee.

"This is an extremely serious situation," said Senator Richard Durbin, who sits on the committee.

"In their effort to seek political revenge against Ambassador Wilson for his column, they are now attacking him and his wife and doing it in a fashion that is not only unacceptable, but may be criminal," the Illinois Democrat said.

"That, frankly, is as serious as it gets in this town," he said.

The Senate Intelligence Committee's top Democrat, Jay Rockefeller, said an investigation might be in order.

"At the very least, it was a highly dishonorable thing to do," Rockefeller said.

The question of an official probe, he said, "is still very sensitive, because we're still trying to find out if the kind of position she holds at the CIA is the kind of thing which, if revealed, would reveal sources and methods ... or put lives in danger."

Rockefeller said it was a time-honored tactic by the Bush administration.

"They go after the people they don't like," the West Virginia Democrat said. "Wilson's a good example of it."

US officials claimed that Iraq possessed banned chemical, biological and nuclear weapons as they sought UN approval to invade Iraq on the grounds that the Gulf nation posed an immediate threat to the United States.

Officials cited as proof a British intelligence report that Saddam Hussein was trying to acquire nuclear materials from Niger, and used the claim in the president's State of the Union speech last January.

White House officials have since said it was a mistake to use the now discredited claims.

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