David Cameron will risk the wrath of Tory backbenchers by making the European Union a key part of his vision for Britain's future.
The prime minister is to stress the importance of being at the "top table" in institutions such as the EU, saying membership is in the national interest.
The intervention comes in a speech in Essex today, billed as setting out the UK's role in the world ahead of the G8 conference in Northern Ireland.
Cameron will argue that the Government is in a "battle for Britain's future", blaming Labour for "passing the buck".
He will acknowledge the pain of austerity, but insist the country has started reforming "just in time" with a "complete plan for national renewal".
"At home, ambitious about competing. Abroad, ambitious about pursuing our national interest and standing up for our values," Cameron will say.
Highlighting some key Conservative dividing lines with Labour, the prime minister is to say: "We have identified, very clearly, our key areas of national weakness compared to the rest of the world.
"One - our debt-fuelled, unbalanced economy. Two - our bloated welfare system. Three - our under-performing education system.
"These are the priorities that define and drive our domestic agenda. A stronger economy. Welfare that works. A world-class education system. And we are pursuing them with ruthless ambition for everyone in this country."
Cameron will cite changes to the planning system, the welfare shake-up and restrictions on non-EU migration among the coalition's achievements.
"Three years into government and we have shaped a coherent and urgent response to the modern world we live in," he will say.
"I do not claim that we have done all we need to, or that we're on the home straight. Far from it. These are still difficult times. We are adjusting as a country; going through a necessary time of change. And while times are hard, there will be those who offer easy answers - where there are none.
"Those who offer the comfort blanket of British destiny - as though we'll always just muddle through.
"The truth is that today, for our country, there is no such thing as destiny, only our determination to succeed. But together we are showing that determination.
"We are taking the right decisions, in this generation, for our country to succeed. This is the generation that hasn't passed the buck. Where there has been a fork in the road between doing what is easy and doing what is right, we have chosen what is right.
"We have started changing our country just in time, equipping Britain to succeed in the modern world. And our drive for Britain to succeed - it is not a case of who's up or down in some global game. It is about the British people and their lives.
Cameron will insist he has a "very clear vision" of the country he wants to live in, where everyone has opportunities.
Turning to Britain's connections abroad, the prime ,inister will make an apparent reference to his pledge of an in-out EU referendum if the Tories win the general election, saying his policy on the issue is "clear".
But he will also echo one of the most common arguments deployed by supporters of EU membership.
"This country depends for its living on international ties and global trade," he is to say. "They in turn depend on global stability and security. And on there being global rules to abide by.
"This is the key point: When your prosperity is won in far-flung places, when your fortunes are disproportionately affected by what happens beyond your borders then your national interest is not just about standing up for yourself - but standing up for what's right, and standing for something more...
"Another key part of that effort is our place at the top table. At the UN. The Commonwealth. NATO. The WTO. The G8. The G20.
"And yes - the EU. Membership of these organisations is not national vanity - it is in our national interest.The fact is that it is in international institutions that many of the rules of the game are set on trade, tax and regulation.
"When a country like ours is affected profoundly by those rules, I want us to have a say on them." However, that does not require "supinely going with the flow of multilateral opinion".
"At the European Union we are prepared to stand up for Britain's interests with resolve and tenacity," he will add.