“To step back now would force a collapse of the Iraqi government,” Mr. Bush said from the White House library, a room officials said was chosen to create more of a sense of a conversation with an anxious American public, rather than the formal surroundings of the Oval Office.  “Such a scenario would result in our troops being forced to stay in Iraq even longer, and confront an enemy that is even more lethal,” he said. “If we increase our support at this crucial moment, and help the Iraqis break the current cycle of violence, we can hasten the day our troops begin coming home.”  Yet for the first time, Mr. Bush faces what could become considerable political opposition to pursuing the war. Democrats in Congress are drawing up plans for what, at a minimum, could be a nonbinding resolution expressing opposition to the to the commitment of more forces to what many of them say they now believe is a losing fight. They are likely to be joined by some Republicans, and they may attempt other steps to block Mr. Bush from deepening the American commitment.  Not since President Richard M. Nixon ordered American troops in Vietnam to invade Cambodia in 1970 has a president taken such a risk with an increasingly unpopular war.  In his 20-minute address, Mr. Bush said that for the first time Iraq would take command-and-control authority over all of its own forces, and he argued that while more Americans ground troops are being put into the field, they will take more of a background role.  He said the Iraqi government was committed to a series of “benchmarks” — which include adding another 8,000 Iraqi troops and police officers in Baghdad, passage of long-delayed legislation to share oil revenues among Iraq’s sects and ethnic groups, and a $10 billion jobs and reconstruction program, financed by the Iraqis.  In a running series of large and small briefings for reporters that opened a major campaign to market the new strategy, Mr. Bush’s aides insisted that the plan was largely created by the government of Prime Minister Nuri Kamal al-Maliki.  Yet Mr. Bush sounded less than certain of his support for the prime minister, who many in the White House and the military fear may be intending to extend a Shiite power over Sunni Arabs or could prove incapable of making good on his promises. “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,” Mr. Bush declared.  The president put it far more bluntly when leaders of Congress came to visit Mr. Bush at the White House earlier today. “I said to Maliki this has to work or you’re out,” the president told the Congressional leaders, according to two officials who were in the room. Pressed on why he thought this strategy would succeed where previous efforts had failed, Mr. Bush shot back: "Because it has to."  Until this summer, Mr. Bush had used the phrase “stay the course,” to describe his approach in Iraq, and his decision to describe his new strategy as an effort to “change America’s course” appeared intended to distance himself from that old approach.  An earlier plan unveiled in November 2005 had been entitled a “Strategy for Victory in Iraq,” but Mr. Bush used the word “victory” sparingly tonight, and then only to diminish expectations.  “The question is whether our new strategy will bring us closer to success,” he said. “I believe that it will,” saying that if it is successful it would result in a “functioning democracy” that “fights terrorists instead of harboring them.”  In some of his sharpest words of warning to Iran, Mr. Bush accused the Iranian government of “providing material support for attacks on American troops” and vowed to “seek out and destroy the networks providing advanced weaponry and training to our enemies.”  He left deliberately vague the question of whether those operations would be limited to Iraq or conducted elsewhere, and said he had ordered the deployment of a new aircraft carrier strike group to the region, where it is in easy reach of Iranian territory.  While Mr. Bush has previously vowed to work diplomatically, largely inside the United Nations to stop Iran’s nuclear program, in this speech he said nothing about diplomacy.  A new defense secretary, Robert M. Gates, who replaced Donald H. Rumsfeld, is among the new members of the Iraq team whom Mr. Bush has brought in to execute the strategy announced tonight. In the past week, Mr. Bush has sped the removal of the American commander in Iraq, Gen. George Casey, who is to become the Army chief of staff, and replaced him with a counterinsurgency specialist, Gen. David Petreaus, who has embraced the new plan.  A new American ambassador has been nominated to Baghdad as well, to replace Zalmay Khalilzad, a Sunni of Afghan heritage, who will represent the United States in the United Nations.
President Bush announced tonight that he is sending more than 21,000 troops to Iraq, while conceding that he provided neither enough troops nor enough resources to control the chaos last year.