Cheney is accused of pressuring the CIA before war to beef up weapons evidence

Dick Cheney, the Vice-President, and his Chief of Staff Lewis Libby made several visits to the CIA in the months before the Iraq war - which some analysts see as attempts to pressure analysts to bolster calls for military action.

The revelation of Mr Cheney's forays to CIA HQ, revealed by The Washington Post, come as the controversy intensifies over whether intelligence was misrepresented to justify the war.

Two Senate committees are considering a joint investigation, and Ray McGovern, a former intelligence specialist and member of Intelligence Professionals for Sanity (IPS), said that intelligence used to sell the war "was manipulated, forged or manufactured".

Mr Bush entered the fray yesterday, vowing to "reveal the truth" about Iraq's WMD programme. "Saddam Hussein's got a big country to hide them. Well, we'll look," he told troops in Qatar, the last stop on a foreign trip before his return to Washington and the mounting controversy.

The visits by Mr Cheney to the CIA will cement the impression that specialists were left in no doubt that hawks expected findings that bore out their views.

Last week George Tenet, the CIA director, took the rare step of issuing a public statement defending the quality of his agency's product on Iraq. In an equally unusual appearance before the press, Douglas Feith, the Undersecretary of Defence for Policy, denied that the Pentagon had pressured the CIA to slant its assessments to help the hawks' case.

Much of the fingerpointing is being directed at the Office of Special Plans, a unit under Mr Feith that was set up to review intelligence after the 11 September terrorist attacks.

In fact, it appears to have turned into an in-house ginger group, tied to Donald Rumsfeld, the Defence Secretary, and his deputy, Paul Wolfowitz, and focussed on making the case for links between Saddam and al-Qa'ida and for Iraq's active pursuit of nuclear arms.

Mr Feith has rejected what he called a "goulash of inaccuracies", promising to "lay to rest stories that are not true and are beginning to achieve the status of urban legend".

However, Mr Feith's theses were publicly undercut last week by Richard Perle, a leading member of the neoconservative group that has been driving Iraq policy under Mr Bush and until recently the chairman of the influential Defence Policy Board.

Defending the Office of Special Plans, Mr Perle said that a lot of mistakes had been made by intelligence analysts. The new unit's job was to see whether "there were connections... that had been missed in previous examinations. That is not politicisation. That is not pressure. And the fact is they established beyond any doubt connections that had gone unnoticed in previous analysis".

This argument is flatly rejected by the veteran analysts of IPS, who describe what happened before the war as "an intelligence fiasco of monumental proportions", in which evidence had been manipulated to sway Congress in its crucial resolution last autumn that granted Mr Bush virtual carte blanche to deal with Iraq.

Even so, the furore here has not reached the proportions it has in Britain. Mr Bush's popularity is high, and as long as it remains so, his party's control of Congress should ensure that hearings do not become too embarrassing. But that could change if Iraq descends into chaos and US forces suffer mounting casualties.