THE US vice-president, Dick Cheney, is expected to come under pressure over his role in the outing of Valerie Plame, the former CIA agent, when she testifies before Congress this week.

It was Plame’s exposure - after her husband Joseph Wilson accused the White House of manipulating prewar intelligence over the supposed sale of yellowcake uranium ore to Iraq - that led to the conviction last week of Lewis “Scooter” Libby, Cheney’s top aide, for lying and obstruction of justice.

Jurors felt they had punished only the “fall guy” for the affair after Patrick Fitzgerald, the special prosecutor, said in his closing remarks that there was “a cloud over the vice-president”.

Plame is bringing a civil case against Cheney, Karl Rove, President George W Bush’s aide, and other officials for revealing her identity. It is a crime to leak the name of a covert CIA agent, although Plame’s precise status has never been revealed.

“This case doesn’t end with Mr Libby’s conviction,” said Maurice Hinchey, a Democratic congressman. “Testimony in the Libby trial made it even more clear that Vice-President Dick Cheney played a major role in Mrs Wilson’s outing.”

The case had revealed that Cheney blamed Plame for proposing that her husband be sent to Niger to investigate the yellowcake allegation. On his return Wilson became a vocal war critic and thorn in the side of the Bush administration.

Denis Collins, a juror, wrote last week about his disappointment that the vice-president had not been called to testify: “We didn’t know what he might reveal. But figuratively he was the last of the seven veils and we would have liked a good look.”

Cheney and his wife Lynne were greeted with a standing ovation when they arrived on friendly turf at the American Enterprise Institute’s black tie dinner last week. One diner recalled: “I dared a friend to yell, ‘Pardon Scooter!’, but he said he hadn’t been drinking enough.”

Despite the friendly reception, there is unease among conservatives about Libby’s fate. Cheney once scribbled a note to himself, “Not going to . . . sacrifice the guy who was asked to stick his neck in the meat grinder because of the incompetence of others.” However, Cheney and Bush are refusing to comment on the case while Libby appeals against the verdict.

Fred Barnes, an editor at the conservative journal The Weekly Standard, believes Libby will ultimately be pardoned by Bush, but said: “We’re all guessing.”

“The White House regards the case not as an institutional problem but as a private problem for Libby,” Barnes added. “When he was indicted the White House was totally in fear. They didn’t know whether Karl Rove would be indicted or Dick Cheney would be indicted as a co-conspirator. Their feeling is it could have been a lot worse.”

Cheney has gone from being a highly regarded asset to Bush on his election in 2000 to being perceived as one of his biggest liabilities. Since he shot a hunting companion last year his reputation has declined. His daughter has been criticised by evangelical Christians for having a baby with her girlfriend, the Taliban mounted an apparent assassination attempt against him last month and last week doctors found a blood clot in his leg, prompting speculation that he could stand down on medical grounds.

His influence on foreign policy is on the wane as Condoleezza Rice, the secretary of state, has quietly redirected it towards negotiations with states such as North Korea and Iran.

Henry Waxman, the Democratic chairman of the government reform committee , is determined to haul Cheney over the coals about contracts in Iraq awarded to Halliburton, his old firm, as well as the Plame controversy.

While there was a brief “dump Cheney” movement among conservatives before the 2004 election, he is thought likely to remain in office as attention shifts to the 2008 Republican presidential nomination.

Norman Ornstein, an expert on Congress at the American Enterprise Institute, said it was premature to write off Cheney: “He still has a one-to-one private lunch with the president every week where he can give his unvarnished advice. It’s a pretty good definition of power.” Congress, he added, had plenty of opportunities to cause Cheney grief but, paradoxically, the administration’s problems could save him: “Just figuring out what to do with the war and the [troop] surge is going to take up a huge amount of time and resources. There is so much exploding out there that it may be good news for him.” oChuck Hagel, the most outspoken Republican opponent of the Iraq war, is expected to announce tomorrow that he is to run for president. The Nebraska senator is popular with colleagues and regarded as a staunch conservative on almost every issue but the war.

Cheney said recently that while he supports the “11th commandment” - thou shalt not speak ill of a fellow Republican - “it’s very hard sometimes to adhere to that where Chuck Hagel is involved”.

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