Condoleezza Rice, the US secretary of state, and David Miliband, the British foreign secretary, have joined Afghanistan's president in stepping up calls for Nato allies to provide more troops to the country.
Rice said she sees progress in the conflict in Afghanistan despite a determined effort by Taliban forces.
Rice said during a news conference in Kabul on Thursday: "Can we all expect the security situation will still be difficult? Yes, because Afghanistan has determined enemies who laid waste to this country over a period of a decade."
Hamid Karzai said he was grateful to all the Nato members for their contributions to Afghanistan's progress, development and stability, but still called for more soldiers on the ground.
As he called for more troops he said that he would leave "the decision [for troop enhancements] to the military men within Nato".
Nato
While Rice and Miliband are in Kabul, Nato members are meeting in the Lithuanian capital, Vilnius, to assess their long-term strategy in Afghanistan.
James Appathurai, a Nato spokesman, told Al Jazeera, that troop contributions are a "long-term effort".
Appathurai was speaking in response to comments by Robert Gates, the US defence secretary, that Nato's input in Afghanistan showed "a lack of commitment".
He said that Nato "is in it for the long-haul", adding that there are today 10,000 more troops in Afghanistan than there were a year ago, confirming that the country currently hosts 43,000 Nato troops.
Appathurai defended the coalition, saying that saving Afghanistan was a "team effort" and that the world's most powerful countries should all work together for a better Afghanistan.
Thursday's surprise visit to Afghanistan comes after Rice and Miliband increased pressure on Nato allies to provide more troops, arguing that the alliance faces a huge battle against the Taliban.
Rice and Miliband also flew to Kandahar, the former Taliban stronghold in the south
Miliband said international efforts to stabilise Afghanistan were entering a "new phase" which combined military solutions with political and developmental concerns.
The Nato-led International Security Assistance Force has 43,250 troops in Afghanistan. The US has a further 14,000-plus troops outside the Nato force.A country-wise breakdown:US: 15,000 troops (mainly east)UK: 7,800 (mainly south)Germany: 3,210 (north)Italy: 2,880 (west and Kabul)Canada: 2,500 (south)The Netherlands: 1,650 (south)France: 1,515 (Kabul)Poland: 1,100 (mobile)Australia: 1,070 (south)Other countries: Denmark (780); Spain (740); Turkey (675); Romania (535)