Barack Obama was joined by British officials in admitting that Afghanistan could be left unstable and vulnerable to terrorist activity once the Nato-led troops leave the country in less than two years.
As the US President said that "bad moments" were likely to come in the course of the alliance's withdrawal, an unnamed UK official was quoted as saying that it was "unrealistic to assume that Afghanistan is going to be completely secure and there is no possibility of a terrorist threat re-emerging".
The comments came as the Nato summit in Chicago veered off script yesterday, as attempts to resolve Pakistan's blockade of Afghan supply routes fell apart and Mr Obama warned the country's leaders: work with us or run the risk of being "consumed by the extremism" that is in its midst.
The Pakistani President, Asif Ali Zardari, had been invited in the expectation he could be persuaded to re-open the routes shut after a Nato raid killed 24 Pakistani soldiers last November. But, with no sign of a resolution, he suffered a rare diplomatic snub when the US ditched plans for a formal one-on-one meeting with Mr Obama.
Nato leaders agreed at the summit that the war in Afghanistan would be over by December 2014 and the lead combat responsibility for the entire country would shift to Afghan forces as early as next summer.
The failure to resolve the supply routes issue was vexing for any country in the International Security Assistance Force (Isaf), including Britain, as the focus shifts to getting supplies out of the country. "We need one of these routes open and functioning to get our equipment out. Pakistan is the most obvious route," the British official said.
Mr Obama, who did exchange brief words with Mr Zardari in a corridor, conceded that the US needs "to work through some of the tensions that have inevitably arisen". While he said the US and Pakistan were making "diligent progress" on the issue, he also adopted a sterner tone: "I don't want to paper over real challenges there... it is in Pakistan's interest to work with us to make sure they themselves aren't consumed by the extremism that is in their midst."
David Cameron also voiced frustration on the Pakistan stand-off. "Obviously we want those lines... open again. I believe they will be, but clearly it's not going to happen today," he said. Diplomatic sources here said that Pakistan felt "seriously bruised" still about the November incident as well as about ongoing drone strikes by the US on its territory and resolving the stand-off may take a long time. Not helping are Pakistan's demands that fees it imposes on supply trucks passing through the border checkpoints be increased from around $300 (£190) as it was before to $5,000 per lorry.
Mr Cameron was under pressure to explain why, in spite of the pledge to formally to end the war in December 2014, plans were also being made to keep a British presence in Afghanistan, even if on a scale far removed from today. British operations beyond the end date would include the training of Afghan officers, referred to as a "Sandhurst in the sands", and a presence, probably SAS-led, to maintain counter-terrorism efforts.
Before leaving Chicago, Mr Cameron conceded that Britain cannot expect to wash its hands of Afghanistan 30 months from now. "We will maintain our commitment to a stable Afghanistan by training, advising and assisting the Afghan National Security Forces post-2014," he said. "We are making a decisive and enduring commitment to the long-term future of Afghanistan. The message to the Afghan people is that we will not desert them. And the message to the insurgency is equally clear: you can't win on the battlefield; stop fighting and start talking."
The problems associated with Afghanistan dominated the summit, which was attended by 62 nations. For public consumption, officials attempted to emphasise progress that has been made in shifting responsibility for security in the country to Afghan soldiers and polices. Soon they will be in the lead, securing about 75 per cent of the country.