Gordon Brown set a deadline of the middle of next year for "turning the tide" against the Taliban yesterday - suggesting that could be when British troops start coming home.
The Prime Minister insisted the Nato campaign had to deliver swift results as a key conference in London agreed a process for giving the Afghan government responsibility for security.
The communiqué issued by the high-level gathering called for a gradual handover starting from the end of this year. Kabul should assume full control over security in the troubled country within five years, according to the document.
Kicking off the event yesterday morning, Mr Brown admitted that 2009 had been "difficult" and there would be "more tough times ahead".
"All our forces have made great sacrifices, with hundreds of lives lost and thousands of casualties sustained," he told delegates. "In the last year Britain alone has suffered over 100 fatalities.
"But these sacrifices are not in vain - all the countries represented here recognise that this campaign is vital to our own national security, to the stability of this crucial region, and to the security of the world."
The leaders - including US Secretary of State Hillary Clinton - set a target for Afghan security force numbers to top 300,000 by October 2011, complementing Nato's military "surge" that will see around 135,000 troops on the ground.
The conference also pledged $140 million of funding for plans put forward by Afghan President Hamid Karzai to reintegrate Taliban fighters who are prepared to renounce violence. A 'loya jirga' - or grand assembly of elders - is to be held in Afghanistan to try to bring more people into the effort to rebuild the country.
Mr Brown stressed the need for quick progress, stating: "By the middle of next year we have to turn the tide in the fight against the insurgency and also in our work to support the Afghan Government in winning the trust of its people."
In a round of broadcast interviews after the conference, he went further when asked exactly when UK troops could start coming home. "By the middle of next year we will have a number of provinces and districts that are ready to be transferred to the security control of the Afghanistan people," he replied.