Europe and the US must heal their divisions over Iraq and work together on winning the peace, Tony Blair has said in a speech.
Tony Blair is upbeat about links with America and Europe
The prime minister told the Lord Mayor's Banquet that anti-Americanism and Euroscepticism made Britain weaker.
His plea came as a poll suggested many people think the UK gains nothing from his close ties to US President Bush.
With Mr Bush on a state visit to the UK next week, Mr Blair urged critics to focus on helping Iraqis.
He said Iraq was of "seminal" importance and would define relations between the West and the Muslim world.
Plans for closer European defence co-operation have caused concern in some sections of the American administration.
Mr Blair said fears the plans might undermine Nato were ill-founded and he was trying to reassure concerns on both sides.
His speech was aimed at reaffirming the "twin pillars" of British foreign policy - the transatlantic alliance and membership of the European Union.
"Take either away and I believe passionately Britain is weaker for it," Mr Blair told business leaders and dignitaries at the Guildhall in the City of London.
He said: "At present, I accept, there is a fairly narrow constituency for this view. The Eurosceptics deride the one. Resurgent anti-Americanism corrodes the other."
Mr Blair said both relationships were in fact in good shape.
But a Populus survey for the Times suggested 60% of voters disapproved of Mr Bush's handling of Iraq.
The poll found only 40% of respondents thought the personal relationship between Mr Blair and Mr Bush benefited Britain. Support for the war came to just 37% of those questioned.
Protests are already planned for Mr Bush's visit next week but Mr Blair said it was exactly the right time for the president's trip.
He said: "What is happening now is very simple. It is the battle of seminal important for the early 21st century. It will define relations between the Muslim world and the West.
"It will influence profoundly the development of Arab states and the Middle East. It will have far-reaching implications for the future conduct of American and Western diplomacy."
Mr Blair said it was people's democratic right to protest against Mr Bush's visit.
But he urged: "Accept that the task now is not to argue about what has been, but to make what is happening now work and work for the very Iraqis we all say we want to help."
Mr Blair hailed the way Iraq was moving towards full democracy with its infrastructure being rebuilt, and said the barrier to progress was "Saddam's small rump of supporters aided and abetted by foreign terrorists".
For that group, a democratic Iraq would mean "the death of the poisonous propaganda monster about America these extremists have created in the minds of much of the world".
While one nation could win a war, said Mr Blair, it took many countries to win the peace.
He went on: "The blunt conclusion is that like it or not, and I do, the EU and US must work with each other. Start from that point and a number of other things fall into place.
"Dismiss the illusion that somehow there is an old and a new Europe, the one opposed to the US and on its way out, the other the bright harbinger of the future to
"Yes, if some try to pull Europe apart from the US, others like us will resist firmly.
"But Europe has too much in common, too many shared interests, too many solid reasons for co-operation, to have any intention of letting a temporary
divergence of view become a permanent rupture."
French antipathy towards America should not be exaggerated, he said.
Mr Blair concluded that with Europe and America together, the world was a "darn sight safer".