Prime Minister Gordon Brown has called for the international community to share the burden of the military campaign in Afghanistan.
It comes during Afghan president Hamid Karzai's visit to Downing Street.
Mr Brown said a combined effort had put the Taleban on the defensive and the strategy for the future was "development, defence and diplomacy".
Nato have appealed for more western troops to make up a shortfall in the alliance's 35,000-strong Afghan force.
Bulwark against terrorism
Mr Brown told a news conference the military campaign in Afghanistan was vital to the fight against terrorism.
"Afghanistan is the frontline against the Taleban," he said.
"We cannot allow the Taleban to be back in control of such an important country. And the work that has been done in the last six years to build a democracy in Afghanistan is an important bulwark against terrorism everywhere in the world."
Mr Brown did not say how long British troops would remain in the country but pledged to work with the Afghan government to make sure its people have a stake in the country's future.
Mr Karzai thanked Britain for its support in the last six years.
His country, he said, had moved forward with new roads, raising of the army and police, a rural development programme, better schools and hospitals and an improved economy.
But problems of narcotics, drug cultivation and the war against terrorism persisted, he added.
Nato defence ministers meeting in the Netherlands for a second day will hear calls for more troops, helicopters and other equipment to be sent to Afghanistan.
The US has voiced growing concerns that European Nato members are not doing enough in the country.
National caveats currently prevent some countries - such as Germany, Italy, France and Spain - from either fighting, or from being based in the more dangerous provinces.
Meanwhile, US, UK, Canadian and Dutch troops are unhappy about bearing the lion's share of fighting a revived Taleban, the BBC's Caroline Wyatt says.
Robert Hunter, a former American ambassador to Nato, said: "If things get worse, pressure - particularly by the US on other allies - will intensify.
"The next time there's a problem in Europe it may be hard to get the Americans to ride to their rescue," he told BBC Radio 4's Today programme.
At the weekend, the Ministry of Defence made clear Britain was not planning to offer extra troops during the two-day summit at Noordwijk.
Earlier, Nato Secretary General Jaap de Hoop Scheffer said a number of alliance members had offered more resources for the military campaign in Afghanistan.
The exact shape of any new contributions to the International Security Assistance Force (Isaf) of 41,100 in Afghanistan could become clear next month during a meeting at the alliance's headquarters in Belgium.
Currently, the UK has 7,700 troops in the country and are fighting the Taleban in Helmand province, one of the most dangerous areas.
Since 2001, 82 UK troops have been killed on operations.
Meanwhile, Air Chief Marshall Sir Jock Stirrup said the Afghanistan situation can only be resolved politically.
In an interview with Sky News, Sir Jock, head of the UK armed forces, said: "There is a misperception that the issues in Afghanistan, and indeed elsewhere around the world, can be dealt with by military means.
"That's a false perception. The military is a key, an essential element in dealing with these problems, but by and large these problems can only be resolved politically."