Davos, Switzerland (CNN) -- The United States and NATO should withdraw from Afghanistan on the basis of success and not set artificial deadlines for a pullout, Britain's opposition Conservative Party Leader David Cameron told CNN Friday.
Speaking to CNN's Christiane Amanpour from the World Economic Forum in Davos, Switzerland, Cameron said it's important to build on and reinforce success rather than set a deadline for a pullout at some point in the future.
"We want to withdraw troops on the basis of success -- on the basis of an Afghan national army that's able to take control of parts of the country -- rather than believing there are artificial deadlines where we can do these things automatically," said Cameron.
With an election coming later this year, current opinion polls suggest Cameron could become Britain's prime minister.
His remarks come a day after the London Conference on Afghanistan that proposed a $500 million "pay-for-peace" plan designed to convince rank-and-file Taliban to give up the fight.
Cameron's rejection of withdrawal deadlines distances him from U.S. President Barack Obama, who plans to begin withdrawing U.S. troops from Afghanistan in July 2011.
The United Kingdom has joined the United States with a pledge to send more troops to Afghanistan -- 30,000 more from the United States and 500 more from the United Kingdom. The British reinforcements will bring that contingent to about 10,000, roughly one-tenth the size of the U.S. contingent.
Cameron also discussed Britain's relationship with the United States, one he noted is occasionally contentious despite many shared values.
Acknowledging that Britain is the junior partner in the relationship, Cameron said he strongly supports the so-called "special relationship" between the two countries.
"It's not a sentimental one," he said. "I think it's based on some very real things from our history. We fought through northern France together to rid the continent of Nazism. We stood together after 9/11."
The United Kingdom stood by the United States in 2003 when the two countries agreed to invade Iraq to topple Saddam Hussein. Britain's role in the war and the events that led up to it are the subject of a sweeping inquiry currently under way in London.
Former British Prime Minister Tony Blair testified Friday that the United States and Britain had slightly different views about the need for war. Americans favored regime change, while Britain said it was Saddam Hussein's reported aims to acquire weapons of mass destruction.
Cameron said that what matters is not one day's evidence to the inquiry, but whether Britain and its allies learn the lessons of the mistakes that were made in Iraq. "That will be the real test of this inquiry," he said.
"For all that's happened, Iraq is definitely better off without Saddam Hussein and without his brutal regime," said the Conservative Party leader, who voted in favor of war with Iraq.
On economic policy, Cameron also highlighted the importance of tackling Britain's massive budget deficit which, at 13 percent of Gross Domestic Product, is the worst of any major developed country.
He said the deficit is unsustainable and the British people are demanding leadership on this issue.
"We know that if we don't do it, we could end up in a situation like Greece or other countries that are in really serious difficulty."
Greece is trying to tackle out-of-control budget deficits of about 13 percent and soaring public sector debt. And that's raising fears the European Union may have to bail out Athens.
Cameron made no mention of any European bailouts for Britain in his interview with Amanpour.