One of Gordon Brown's senior advisers asked the commander of Nato forces in Afghanistan to play down his concerns over the campaign to avoid damaging the Labour government, according to leaked documents.
The request came as the then-prime minister visited the country and was briefed by US General Stanley McChrystal on the growing threat posed by the Taliban.
A security adviser to the premier is said to have told Gen McChrystal - with Mr Brown present - that his "bleak assessment" could result in negative press coverage.
At the time, the government was under pressure over equipment shortages and high casualties suffered by British forces.
A US diplomatic cable, passed to the Daily Telegraph by the WikiLeaks website, makes clear that the general refused to back down.
"COMISAF (Gen McChrystal) replied that while he was sensitive to that impression, he would maintain his intellectual honesty - and that what might be perceived by some as a bleak assessment might be considered by others to be 'realistic'," it said. "COMISAF stressed that while the situation in Afghanistan was 'serious and deteriorating', the mission could still be accomplished with proper resources and a focus on ANSF (Afghan National Security Forces) expansion and partnering.
"Threats to security emanated from a resilient and growing insurgency, a crisis in confidence toward the government and its abilities and overall questions about Nato commitments. COMISAF said that without additional resources, current efforts would be 'fixed' - but with more resources, enough terrain could be controlled to deny the Taliban strategic traction."
The meeting was held at Camp Leatherneck in Helmand in August 2009. Just over a month later Mr Brown attended a similar meeting in London with David Miliband, then foreign secretary, Gen McChrystal and Admiral Mullen, US chairman of the Joint Chiefs of Staff.
Simon McDonald, then head of foreign and defence policy, asked the Americans to show "sympathy for the pressure" that Mr Brown was under.
Mr Brown "repeatedly and forcefully" underscored the need for Afghan forces to play a much greater role, according to the cables. He said his challenge was "persuading the British people that there was a way forward and not a stalemate".