The US defence secretary has said more time is needed to decide whether to increase troop levels in Afghanistan, BBC reported.
Robert Gates said it would be one of the most important decisions of the Obama presidency.
Last week the top US general in Afghanistan said the operation was "under-resourced" and a "dramatically different" strategy might be needed.
Mr Gates said the president welcomed candid advice on Afghanistan, but added that it should be made in private.
The security situation in Afghanistan is continuing to deteriorate, with Mr Gates saying the war was on a "worrisome trajectory".
On Sunday, eight US soldiers and two Afghan troops were killed in Nuristan province in the deadliest attack on coalition troops for more than a year.
'Chain of command'
Barack Obama met Gen Stanley McChrystal, the top US and Nato commander in Afghanistan, on Air Force One in Copenhagen last week as debate continues on the future strategy of troop deployment in Afghanistan.
Mr Gates did not refer directly to the general but said: "It is imperative that all of us taking part in these deliberations, civilians and military alike, provide our best advice to the president, candidly but privately."
Mr Gates, in his speech to the Association of the United States Army annual meeting in Washington, stressed that the decision on increasing troop numbers would be vital.
"So it is important that we take our time to do all we can to get this right."
The defence secretary is believed to have an open mind on the direction on Afghan strategy.
His comments come after the president's national security adviser, former Gen James Jones, also urged more caution on remarks on the matter.
Gen Jones, in what was seen as a mild rebuke of Gen McChrystal, said it was "better for military advice to come up through the chain of command".
Gen McChrystal had described the situation in Afghanistan as "serious" and is believed to have requested up to 40,000 additional troops.
At the weekend, the new head of the British Army backed calls for more international forces.
Gen Sir David Richards told the Sunday Telegraph reinforcements would enable Nato to achieve its objectives more quickly and with fewer casualties.
Mr Obama has said the strategy in Afghanistan must be agreed before a decision can be made on troop numbers.
Gen McChrystal is believed to want the focus of the strategy to fall on protecting the Afghan people and carrying the fight to the Taliban.
But an alternative would be to concentrate on targeting al-Qaeda and increasing covert operations and unmanned drone attacks.
Vice President Joe Biden is believed to favour this approach.
The strategy will be discussed in a series of Obama administration meetings this week.