French President Nicolas Sarkozy and British Prime Minister Gordon Brown vowed to boost cooperation on the economy and immigration as Sarkozy began a visit aimed at improving awkward ties.
Sarkozy, speaking of "Franco-British brotherhood," said he would ask Brown's help in getting Washington to halt a plunging dollar, which is making European exports more expensive. Britain has typically shunned managing foreign exchange levels, saying markets are the best guide.
Brown, who will hold talks with Sarkozy on Thursday, said a new era was dawning for the "entente cordiale" -- a treaty signed by the two countries more than a century ago -- in which Britain and France would speak as one on international economic reform.
The two neighbors, though bound together by mainstream European institutions like the European Union and NATO, have a love-hate relationship of deep mutual suspicion going back centuries.
But in an increasingly global world their economies now overlap in every sphere.
The French president, accompanied by his new wife, former model Carla Bruni, will stay with Queen Elizabeth, address parliament and meet Brown as he seeks to build a stronger alliance with Britain during a two-day state visit.
"I want a new Franco-British brotherhood," Sarkozy told the BBC in an interview, sketching a vision of far-reaching cooperation on the economy and defence that goes beyond anything Britain is envisaging.
"Why don't we pool our arms industries so that we spend less money and be more effective?" Sarkozy said.
"Couldn't we better define an immigration policy? ... On the economy, couldn't we try and get the Americans to agree to do something about their dollar?"
"Often it is our differences that are underlined and underscored ... but we enjoy the same music, we like reading the same authors, we have the same enemies throughout the world, we have the same aspiration," Sarkozy said.
Sarkozy was welcomed by Queen Elizabeth with a state carriage procession to Windsor Castle near London. It is the first state visit by a French president since Jacques Chirac came in 1996.
Brown and Sarkozy have struck up a good relationship since both came to power last year. But the popularity of both leaders has dropped after solid starts. Sarkozy's standing has sunk since he married Bruni, a fashion model-turned-singer, last month.
Several British newspapers marked the visit by printing an old picture of Bruni posing nude.
Sarkozy has sought to improve relations with the United States and Britain, strained by the U.S.-led invasion of Iraq in 2003, which Chirac resisted.
Some political analysts say Sarkozy is reaching out to Britain because he does not get on well with German Chancellor Angela Merkel. Berlin and Paris traditionally dominate the European Union.
Brown, speaking in parliament, said the historic "entente cordiale" between the two countries was moving into a new era.
"I believe in the international institutions ... we will now vote together on crucial areas where we've got to reform the international economy," he told parliament.
British officials say Brown and Sarkozy, due to hold talks on Thursday at football club Arsenal's stadium, will urge banks to disclose fully write-offs caused by the global credit crisis.
Brown said he hoped the two countries would agree to tighten controls on illegal immigration at the French port of Calais.
The two men may not see eye-to-eye on defense.
Sarkozy has signalled France might be ready to return to NATO's military structures after 41 years' absence but insists on strengthening the EU's defence capabilities.
Britain opposes any moves that undermine NATO, but Brown suggested on Wednesday the EU could do more civilian reconstruction work, complementing NATO's military work.
France and Britain will also call for reform of the U.N. Security Council to make it more representative, including permanent representation for Africa, British officials say.