Tony Blair will use a Cabinet reshuffle to try to regain momentum after Labour's losses in the English local council elections.
Will Charles Clarke and Patricia Hewitt kiss goodbye to government?
Ministers have been put on standby for the shake-up and attention will be on whether under-fire Home Secretary Charles Clarke will hang on to his job.
Some Labour MPs are pressing Mr Blair to set out the timetable for his departure from Downing Street.
Opposition parties say the reshuffle is just a diversionary tactic.
Labour has so far suffered net losses of more than 200 council seats and lost control of 17 local authorities.
A post at the Cabinet Office has been vacant since John Hutton replaced David Blunkett as work and pensions secretary.
The extent of the reshuffle is not clear but the Conservatives and Liberal Democrats have repeatedly called for the home secretary to be sacked over the foreign prisoners controversy.
Deputy Prime Minister John Prescott's Cabinet job is also under the spotlight after the storm over his affair with a secretary.
Mr Prescott was earlier seen going into Number 10.
Health Secretary Patricia Hewitt is another minister who has been under pressure since being booed by nurses angry about deficits at NHS trusts.
Commons Leader Geoff Hoon said he would be heading to see Mr Blair early on.
Mr Hoon told the BBC: "There is always a reshuffle at at around this time of the year - perhaps slightly earlier than normal.
"There is a vacancy in Cabinet... We've had these elections, time now for a new team to take over."
Shadow chancellor George Osborne said: "This reshuffle is an attempt to cover up very bad losses for Tony Blair and Labour in the local elections and very good results for David Cameron and the Conservative Party."
Some Labour backbenchers believe Mr Blair must go further than just overhauling his team.
Former Health Secretary Frank Dobson said a reshuffle would be like "rearranging the deckchairs on the Titanic".
"Quite frankly we need the party under new management," said Mr Dobson.
He said he had told Mr Blair after the last general election that he had become a liability and Labour would receive a drubbing at the local elections if he continued in office.
"That's what happening now," he added.
'No more drifting'
There are rumours that a letter is circulating among Labour backbenchers urging Mr Blair to stand down.
Reading MP Martin Salter called for a "clear timetable" for the "orderly transition" from Mr Blair to his successor.
He said: "I want to know where we are going to be. I want whoever is the new leader of our party - and we are going to have one before the next general election - to have plenty of time to bed in, because we have got to put these difficult periods behind us."
Ex-minister Nick Brown, a close ally of Chancellor Gordon Brown, said the government had to show it was not a "complacent elite" and could not "drift on".
Asked if Mr Blair could turn Labour's fortunes round, he replied: "I don't know but he has got to try."
'Not as bad as feared'
Culture Secretary Tessa Jowell said she was sorry if local activists felt let down by ministers after the recent controversies.
But she argued that a poor set of results would not be a "watershed moment".
She told Sky News: "We've been in power for nine years and all governments go through rough periods. This is a rough period."
Defence Secretary John Reid said the results had not been as bad as he initially feared.