Congressional Democrats are leading the criticism of President Barack Obama's plan for withdrawing US troops from Afghanistan, arguing that his timeline for bringing 33,000 home by next summer is too slow.
However, some Republicans fear the withdrawal will be too fast and the top US military officer said the plan is riskier than he originally considered wise.
An initial pullout of 10,000 troops is expected to take place in two phases, with 5,000 troops coming home this summer and 5,000 more by the end of the year. An additional 20,000-plus are to follow by September 2012.
That still would leave about 70,000 US troops in Afghanistan, with many to come home gradually over two more years.
"It has been the hope of many in Congress and across the country that the full drawdown of US forces would happen sooner than the president laid out - and we will continue to press for a better outcome," said house minority leader Nancy Pelosi, leading a chorus of disgruntled Democrats.
From across the political divide, the Republican response to Obama's timeline for withdrawing tens of thousands of troops was measured.
House Speaker John Boehner, a Republican, warned Obama not to sacrifice the gains the US has made in Afghanistan, while Senator John McCain said the withdrawal was too rash.
"This is not the 'modest' withdrawal that I and others had hoped for and advocated," Mr McCain said in a statement following Mr Obama's prime television time address to the nation on Wednesday night.
"It seems the president is trying to find a political solution with a military component to it, when it needs to be the other way around," Rep. Mike Rogers, the Republican chairman of the House Intelligence Committee, said.
Navy Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, told Congress that he supports the president's plans, but they are "more aggressive and incur more risk" than he had considered prudent.