U.S. President George Bush has announced his plan to boost troop numbers in Iraq as part of a new strategy to curb sectarian violence.

In his nationwide address on Wednesday night, Bush warned the U.S. commitment is not open-ended and said it's time for the Iraqis to step up.

The American president also admitted that mistakes have been made and insisted that his plan would redress those errors.

"Our past efforts to secure Baghdad failed for two principal reasons," Bush said from the White House.

"There were not enough Iraqi and American troops to secure neighbourhoods that had been cleared of terrorists and insurgents, and there were too many restrictions on the troops we did have."

Bush also said that "where mistakes have been made in Iraq, the responsibility rests with me."

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.

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.

But analysts say the new strategy is largely dependent on Iraqis taking a far more active role in stabilizing their country.

"The Iraqis have to step up," White House counsellor Dan Bartlett said.

Bartlett said that the rules of the past, where for instance U.S. forces in Baghdad "sometimes were handcuffed by political interference by the Iraqi leadership," must end.

"They (the Iraqis) are going to have more boots on the ground," he said. "They're going to be the ones doing the knocking on the door."

The president also stressed the importance of Iraqi action during his speech, saying that "America's commitment is not open-ended. If the Iraqi government does not follow through on its promises, it will lose the support of the American people and it will lose the support of the Iraqi people. Now is the time to act."

Here is a breakdown of the 21,500 additional troops heading to Iraq:

  • Bush is committing 17,500 U.S. combat troops to Baghdad. The first of five brigades were arrive by next Monday. The next is to arrive by Feb. 15 and the reminder will go in 30-day increments.
  • Another 4,000 Marines will head to Anbar Province, a base of the Sunni insurgency and foreign al Qaeda fighters.
  • The Iraqis are committing three brigades for Baghdad, the first to be delivered on Feb. 1. Two more will arrive on Feb. 15th.

Iraq's Prime Minister Nouri al-Maliki has assured Bush that "this is going to be an operation in Baghdad that will make no difference between Shiite, Sunni or other types of illegal militia or illegal activity," Bartlett said.

The White House anticipates that Baghdad can be stabilized by summer, so that U.S. troops will be able to pull back to areas outside the capital. Iraqis were expected to be in control of security in all 18 of Iraq's provinces by November, the official said.

Among other steps by the United States is expansion of an existing program to decentralize reconstruction efforts. Ten units known as Provincial Reconstruction Teams will be expanded to 19, with the additional units based in Baghdad and in Anbar province, the most violence-plagued parts of Iraq.

The teams, under State Department control, will administer some of the economic aid, including an effort to provide small loans to start or expand businesses.

Iraq study group ignored

Bush is ignoring key recommendations of the bipartisan, independent Iraq Study Group, including that he include Syria and Iran in discussions about efforts to staunch Iraqi bloodshed, the official said.

Instead, he has called for increased operations against nations meddling in Iraq, aimed at Iran and, to a lesser degree, Syria.

The president's address was the centrepiece of an aggressive public relations campaign that also includes detailed briefings for lawmakers and reporters and a series of appearances by Bush starting with a trip Thursday to Fort Benning, Ga.

U.S. Secretary of State Condoleezza Rice, after appearing with Defense Secretary Robert Gates at Democratically convened Iraq hearings on Thursday, heads to the Mideast on Friday.

Since last week, Bush has briefed more than 100 lawmakers -- meetings culminating Wednesday with Congress' Democratic leadership and their Republican counterparts.

Bush also has filled in the leaders of Britain, Australia and Denmark, with more calls planned.

Crafting the new policy took the president nearly three months. Relevant agencies conducted reviews, outside experts were called in, and the president consulted several times with al-Maliki and other prominent Iraqi leaders.

While Bush considered his options over the past few months, the number of U.S. military deaths in Iraq passed 3,000, and Saddam was hanged for atrocities committed under his leadership.

Bush also made major changes in his Iraq team. There are, or will be, new faces running the Pentagon in Washington and the war in Baghdad, a new U.S. ambassador to Iraq, a new top American diplomat at the United Nations and a new top intelligence official.

With files from the Associated Press