David Cameron will deliver his long-awaited speech on Britain's relations with the European Union later this week, Foreign Secretary William Hague has confirmed, insisting there is a 'strong case' for a referendum.
The Prime Minister had been due to make the speech in the Netherlands on Friday but it was postponed due to the Algeria hostage crisis.
"It will happen this week," Mr Hague told BBC1's The Andrew Marr Show. "We will make an announcement on when and where tomorrow."
Cameron has been under pressure from eurosceptic Tories to set out his position on whether he will promise a referendum on EU membership after the next election.
The PM's reticence on the subject has been a source of frustration to many, with the emotive policy threatening to tear a divide in the coalition.
Hague said on Sunday there was a 'strong case' for holding a vote, telling the BBC "fresh consent" would be needed to make Britain's EU Membership a success.
"We want to succeed in the European Union - we want an outward-looking EU to succeed in the world, and for the United Kingdom to succeed in that," he said.
"But we have to recognise that the European Union has changed a lot since the referendum of 1975 and that there have been not only great achievements to the EU's name but some things that have gone badly wrong, such as the euro."
Extracts from Mr Cameron's Netherlands speech showed the Prime Minister intended to make clear that he wanted the UK to play a "committed and active" part in the EU in 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".
The extracts released by Downing Street did not reveal whether the Prime Minister intended to commit himself to an in/out referendum on British membership of the EU following the renegotiation of its terms which he has already said he plans to undertake after the 2015 general election.
The US ambassador to London, Louis Susman, became the latest senior figure to make clear that the Obama administration did not want the UK to break away.
"We believe in a strong EU. We cannot imagine a strong EU without a vibrant partner in the UK," he told Sky News's Murnaghan programme.
"That is what we hope will come about but it is up to the British people to decide what they want."
In December the PM poked fun at himself for delaying the speech, saying "This is a tantric approach to policy-making. It'll be even better when it does eventually come."
Michello Portillo, who served as the Conservative Defence Secretary under John Major and was notoriously eurosceptic during his time in power, said the PM must tread carefully over whether he offers an in or out vote.
“To commit himself to an in-out referendum in the mid term of his next government seems to me to be extraordinarily dangerous,” Mr Portillo told Sky's Murnaghan programme.
“People like to kick their government in the teeth."
Cable’s intervention signals a ratcheting up up of the Lib Dem attack on Cameron’s increasingly eurosceptic position.
Former defence secretary Liam Fox said he would prefer to have a renegotiated relationship with Europe and that ultimately he would like to leave the union.
Dr Fox told BBC One's Sunday Politics programme: "I think ultimately there has to be an in-out referendum because otherwise we're going to have our politics in Britain constantly undermined by this debate and I think it's very important that we settle one way or another the European argument for a generation."
He added that if the choice was between going in the current direction with an ultimately greater and greater loss of British sovereignty, "my personal preference would be to leave".
He said: "I don't want to have ever closer union, I don't want to be a European first and British second."
Eurosceptic Dr Fox added he had been "broadly satisfied" with what he saw that Mr Cameron was intending to say on Europe.
Asked if he was going to return to the Cabinet, he replied: "No I wouldn't say that was true, I've got a lot of things that I'm doing at the moment, but most of us, if asked would you like to be in the Cabinet, would say yes of course we would."
Shadow foreign secretary Douglas Alexander told the same programme Mr Cameron's speech had "more to do with the politics of the Conservative Party...than actually to do with the national interest."
He said: "Why has the speech been delayed for more than a year? David Cameron I would suggest was actually rendered speechless because of the gap between what his backbenchers will tolerate and what European partners will give him."
An alliance between the Conservatives and Ukip is "virtually impossible to even contemplate" with David Cameron as Prime Minister, Nigel Farage said on the Andrew Marr show on Sunday.
Mr Farage claimed pressure from Ukip and its supporters had contributed to a shift in public attitude towards the Europe Union.
He said: "The first thing to say is that 10 years ago you couldn't even discuss the question of leaving the EU in polite society, it was considered completely beyond the pale to even talk about.
"So the very fact that the Prime Minister is making a speech on this issue is actually a tribute to the thousands of people that have worked and helped get Ukip established as a political party."