A top US politician has called for more American troops to be deployed in Iraq to control growing sectarian violence.
Mr McCain said up to 10 more brigades should be sent
Republican Senator John McCain said in Baghdad that up to 30,000 more troops should be sent to stabilise Iraq and also help the political process there.
Mr McCain, a 2008 presidential hopeful, said he agreed with a recent US Iraq Study Group report that the situation in Iraq was serious.
Some 140,000 US troops are currently deployed in Iraq.
Mr McCain's comments come as President Bush is holding a flurry of meetings with top US and Iraqi officials and experts on how to change his Iraq policy.
Mr Bush had been due to announce a new strategy before Christmas, but his speech will not now be made until January.
On Thursday, violence continued unabated in Iraq. In the biggest attack, gunmen dressed in military uniforms seized dozens of people from a commercial area in central Baghdad.
"The situation is very, very serious," said Mr McCain in Baghdad, where a high-level Congressional delegation has been holding talks with US commanders and Iraqi officials.
Mr McCain said Shia cleric Moqtada al-Sadr should be dealt with
"It requires an injection of additional troops to control the situation and to allow the political process to proceed," he said.
He suggested that reinforcements could be five to 10 brigades - about 15,000 to 30,000 troops - to deal with the situation.
Mr McCain also urged both the Iraqi government of Prime Minister Nouri Maliki and the US-led coalition to do more to break the influence of radical Shia cleric Moqtada al-Sadr and his Mahdi Army.
"We should have arrested Moqtada al-Sadr three years ago. He continues to be a major obstacle to peace - his influence in domestic politics needs to be eliminated," he said.
On Wednesday, President Bush said he would not be rushed into deciding how to change his Iraq policy.
Mr Bush admitted the level of violence in Iraq had been "horrific"
Speaking in Washington talks with top Pentagon officials, he said he was receiving advice, but would reject implementing "ideas that would lead to defeat" - such as "leaving before the job is done".
Mr Bush also said he would not give up on the goal of trying to make Iraq a stable democracy.
But he admitted that the level of violence in Iraq, invaded by a US-led coalition in 2003, had been "horrific".
Last week's Iraqi Study Group report said combat troops could be withdrawn from Iraq by early 2008.