The Republicans justified their position by saying the probe, which has been demanded by opposition Democrats, would be used to politicize the problem and use ahead of the 2004 presidential elections.

More than eight weeks since the ouster of Iraqi president Saddam Hussein, the US military is still to find suspected Iraqi weapons of mass destruction, which have been used by the administration of President George W. Bush as the primary rationale for war.

Moreover, CIA representatives have recently anonymously stated to the press that they had felt pressure on the part of the Bush administration to present an analysis of the Iraqi threat that it wanted to see.

Republican Senator Pat Roberts, who heads the Senate Intelligence Committee, said he would not allow the committee "to be politicized or to be used as an unwitting tool for any political strategies."

"About the question of an official, joint investigation: it's very premature," Roberts told a joint press conference with Representative Porter Goss of Florida, and John Warner, chairman of the Senate Armed Services Committee.

Roberts said criticism of the work of US intelligence services would create "divisiveness" with the intelligence committee and the US Department of Defense.

And before any official inquiry was launched, the various committees in charge of supervising intelligence gathering activities would investigate and interview witnesses, he said.

"When the committee deems it appropriate we will make whatever public statements that are necessary," he said.

The Senate Intelligence Committee begins closed-door hearings into the matter next week while the Armed Services Committee has already help three meeting.

The Senate Armed Services Committee's top Democrat, Carl Levin, and top Democrat on the Intelligence Committee John Rockefeller have called for a more official investigation, jointly by the committees of both houses and followed up by the publication of a report.

"You need a structure for an inquiry: what is it we're looking for?" Levin said.

He said the hearings' proceedings should be made public as soon as possible.

According to Levin, the credibility of US intelligence services was at stake.

Rockefeller complained congressional committees were notoriously slow and said he was not certain if Republicans seriously wanted to get to the bottom of what happened to the Iraqi weapons of mass destruction.

Democrats are insisting on a transparent probe and would like its results to be made public.

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