With debate heating up on the unpopular war following a spike in US troop deaths, Obama is under intense pressure to offer lawmakers of both parties more detail on his evolving internal review of Afghanistan policy.

Political temperatures here are flaring as each party advances conflicting approaches, while war commander General Stanley McChrystal has apparently irked the White House by openly campaigning for more troops.

Obama, who came to power vowing to halt the war in Iraq, is facing stiff opposition from some fellow Democrats to the idea of escalating the conflict in Afghanistan.

Republicans are also piling pressure on the president, demanding he quickly meet McChrystal’s reported request for 40,000 more soldiers.

A number of senior Democrats, including powerful House of Representatives speaker Nancy Pelosi, warn there is little appetite among their ranks for adding to the 68,000 US troops who will be in Afghanistan by late this year.

Other leading Democrats, including the powerful head of the Senate Armed Services committee Carl Levin, want the training of Afghan forces accelerated before more US personnel are committed.

Meanwhile a group of Democratic House lawmakers have introduced legislation seeking to block funds for more troops.

One plan reportedly under consideration is shelving mass counter-insurgency operations against the Taliban in favour of using more drones and air attacks against al-Qaeda.