Liberal lawmakers from the US president's Democratic Party have cautioned against sending more troops to Afghanistan, exposing a rift among the US politicians and the army.

This comes as Barack Obama is expected to announce a decision on whether to send more troops to Afghanistan to reinforce the 68,000-strong force who will be fighting there by the end of the year.

"We are concerned about committing additional US troops and taxpayer dollars in Afghanistan, especially when the US mission is unclear and when methods for measuring mission effectiveness are underdeveloped or nonexistent," five members of the Congressional Progressive Caucus wrote in a letter on Tuesday.

The lawmakers, led by Representative Mike Honda of California, called for a “comprehensive rethinking” of the military mission.

They also urged a “complete and courageous redesign” of the reconstruction strategy in the war-torn nation.

Meanwhile, Congresswoman Lynn Woolsey urged the administration to use “smart power” instead of more troops, calling on Obama to devote most US efforts on humanitarian aid, diplomacy, and economic development.

The latest development comes as Obama formulates a new strategy for the deteriorating mission in Afghanistan, before taking a final decision on whether to dispatch another 20,000 to 40,000 troops, as requested by his top generals.

This is when, only this winter, Obama had approved 21,000 more troops to Afghanistan.

During the last months, insurgency has skyrocketed in southern and eastern Afghanistan, where the Taliban has stepped up attacks against US and NATO occupation troops with roadside bombs and ambushes.

Over 400 Western troops have been killed in the fighting in 2009 alone, making it the deadliest year of the war since the beginning of the US invasion of Afghanistan in 2001.

At the same time, Afghan civilian casualties — many of whom killed in the US air raids — have increased dramatically, resulting in greater animosity toward the occupiers.

FF/AKM