Both Democrats and Republicans are criticizing U.S. President George Bush's plan to send thousands of additional troops to Iraq, although other nations have pledged their support.

"I think this speech given by this president represents the most dangerous foreign policy blunder in this country since the Vietnam war," said Republican Senator Chuck Hagel.

Senator Richard Durbin said the president was ignoring the advice of the former US commander in Iraq, Gen John Abizaid, that increasing troop numbers would prevent the Iraqis from taking more responsibility for their own future.

And James Carafano, a military adviser for the Iraq Study Group, told AP that Bush's Wednesday speech failed to discuss the risk involved in the new strategy.

"If anything, I think the president should have been more forthcoming in saying that, 'Look we can do this, it's worth trying to save this country and save this democracy... but we should realize that we can do all those things and we can still fail in Iraq'."

Meanwhile, leaders of South Korea, Australia and Japan have greeted the plan as an essential step towards stabilizing the country and battling global terrorism.

All three pledged to continue providing political and material support for the U.S. efforts.

"If America retreats in Iraq, then that has enormous consequences for the stability of the Middle East and it will also be an enormous boost to terrorism in our part of the world,'' Australian Prime Minister John Howard said in Sydney. Australia has 1,900 troops stationed in and around Iraq.

Howard said Bush's plan was "very clear, calm and above all, realistic."

He also praised Bush's willingness to take responsibility for mistakes made in Iraq.

Unsurprisingly, Iran and Syria have both spoken out against the troops surge.

Iran Foreign Ministry spokesperson Mohammad Ali Hosseini said the troop surge is just a "continuation of occupation" that will "extend insecurity, danger and tension in the country," according to The Associated Press.

Syrian Vice President Farouk al-Sharaa said sending more American troops would only "pour oil on the fire."

On Wednesday evening, Bush announced his plan to boost troop numbers in Iraq as part of a new strategy to curb sectarian violence.

In his nationwide address, he warned the U.S. commitment is not open-ended and said it's time for the Iraqis to step up and do more.

The majority of the additional 21,500 troops slated to be sent to Iraq will work to restore stability in Baghdad, hoping to quell sectarian strife that has pushed the country towards civil war.

Bush spoke with Japanese Prime Minister Shinzo Abe and South Korean President Roh Moo-hyun by telephone before making his announcement, AP reports.

Both countries host large numbers of U.S. troops and have sent forces to Iraq -- though Japan withdrew its 600 non-combat troops last year.

Japan pledged to continue its humanitarian air support for reconstruction, Foreign Minister Taro Aso said. He said Japan would remain in close contact with the U.S.

"I strongly hope that the U.S. efforts toward the stability in Iraq and reconstruction will proceed effectively and bring good results,'' Aso said in a statement. "Japan will continue to closely communicate and co-operate with the U.S.''

South Korea, which has 2,300 troops supporting U.S.-led reconstruction efforts in Irbil in northern Iraq also expressed its support for the new U.S. policy.

The South Korean president "said he understood the background of the comprehensive U.S. policies and expressed support for President Bush's endeavour to bring about stability and reconstruction in Iraq,'' his office said.

Currently, Seoul is Washington's second biggest coalition partner. Britain is the first.

South Korea intends to withdraw 1,100 troops by spring and will devise a complete withdrawal plan during 2007.

Bush has said 80 per cent of violence in Iraq takes place within a roughly 50-kilometre radius of Baghdad, and that the extra troops would help to secure the capital.

ABC News is reporting that the leading edge of the surge has already arrived in Baghdad, including 90 advance troops from the 82nd Airborne division.

With a report by CTV's Tom Clark and files from The Associated Press