David Cameron will make his delayed speech outlining his vision for the UK's future in Europe on Wednesday morning.
Mr Cameron cancelled the much-anticipated speech last week because of the Algeria hostage crisis. He had been due to speak in Amsterdam.
"Wednesday morning in London fits best with the Prime Minister's schedule," a No10 spokesman said.
In the speech, Mr Cameron is expected to spell out plans to renegotiate Britain's membership of the European Union and promise a referendum on any deal he can strike.
Extracts from a speech that Mr Cameron was planning to make show that the Prime Minister intended to make clear that he wants the UK to play a "committed and active" part in the EU in the future.
But he was also planning to warn that, if changes are not made to address the three key challenges of eurozone crisis, economic competitiveness and dramatically declining public support, "the danger is that Europe will fail and the British people will drift towards the exit".
Mr Cameron has won the backing of London mayor Boris Johnson, who said: "We ... want to complete the single market - which everyone supports - and we want to get rid of some of the barnacles that have become attached to the hull."
He has also earned support from former defence secretary Liam Fox - seen as a key eurosceptic - who declared himself "broadly satisfied" with extracts of the speech he had seen.
But Labour leader Ed Miliband warned that the PM was about to take Britain "to the edge of an economic cliff" by creating uncertainty for business, while Vince Cable warned him not to take a "dangerous gamble" with the national interest.
The Business Secretary said there was a risk that Mr Cameron could end up taking Britain out of the EU "by accident".
Eurosceptics in the City, as well as Tory backbenchers, including former Cabinet ministers, have called on Mr Cameron to offer Britain "a clear choice" over its membership of the European Union.
There was a rare intervention on the issue from the US, when assistant secretary for European affairs Philip Gordon made it clear that the White House wanted "a strong British voice" in the EU and said referendums risked turning countries "inward".
More From Sky News