Gordon Brown will pledge to pull the economy through the "storm" of recession as the Treasury is set to confirm March 24 as Budget day.
The date is due to be announced by Chancellor Alistair Darling on Wednesday morning, and the date will make a May 6 general election even more likely.
Treasury officials would only confirm that the date would be published in a written statement to the House of Commons.
Mr Brown will concentrate on one of the key election battlegrounds with what aides are describing as a "major" speech on the economy.
He will defy calls for earlier action to reduce the massive budget deficit, saying: "We are weathering the storm; now is no time to turn back.
"We will hold to our course. And we will complete this mission. We have got through this storm together but there are still substantial risks ahead.
"There will be bumps in the road. And I believe the only way to overcome them is by displaying the same strength and resolve as we did during the crisis."
Mr Brown will be speaking at Thomson Reuters in Canary Wharf, the venue where Tory leader David Cameron attacked Labour's record on the economy last week.
The Tories are determined to make the economy one of the defining issues of the election campaign, arguing that Labour has left voters worse off since 2005.
Mr Brown has been pinning his hopes, at least in part, on the economy bouncing back strongly from the recession in the early months of 2010. Mr Cameron and shadow chancellor George Osborne insist the Government is putting growth and interest rates at risk by delaying moves to bring down borrowing.