The president said that while it's true that Iraq's Saddam Hussein was not connected to the Sept. 11, 2001 terrorist attacks, the decision to oust him cannot be viewed in isolation.
"In a world where terrorists armed with boxcutters had just killed nearly 3,000 people, America had to decide whether we could tolerate a sworn enemy that acted belligerently, that supported terror and that intelligence agencies around the world believed had weapons of mass destruction," Bush said, referring to intelligence reports that later proved false.
"It was clear to me, to members of both political parties, and to many leaders around the world that after Sept. 11, this was a risk we could not afford to take," the president said about the Iraq war, which has claimed the lives of more than 4,200 U.S. military personnel.
In his speech to the annual Saban Forum, a gathering on Middle East policy sponsored by the Brookings Institution, Bush credited the Iraq invasion that deposed Saddam with persuading Iran to suspend its nuclear weapons search. He noted the U.S. intelligence community has timed Tehran's halting of a key part of its nuclear weapons program to 2003 - the year the war began.
"The defeat of Saddam ... appears to have changed the calculation of Iran," Bush said.
More broadly, he defended his administration's approach to diplomacy with Iran, which so far has been unsuccessful. "We have made our bottom line clear," Bush said. "For the safety of our people and the peace of the world, America will not allow Iran to develop a nuclear weapon."
Bush said that after Saddam's regime had been toppled by U.S.-led forces, his administration chose to stand by the Iraqi people, help nurture a budding democracy - even launch a military buildup when increased violence threatened to tear the nation asunder.
"When Saddam's regime fell, we refused to take the easy option and install a friendly strongman in his place," he said. "Even though it required enormous sacrifice, we stood by the Iraqi people as they elected their own leaders and built a young democracy."
Earlier this week, Iraq's three-member presidential council signed off on a new U.S.-Iraqi security agreement, which requires the nearly 150,000 U.S. troops to leave Iraq by January 1, 2012. It also requires American soldiers to withdraw from Iraqi cities by the end of June 2009. On Thursday and Friday, Bush called several Iraqi leaders, including Prime Minister Nouri al-Maliki, to thank them for their work in getting the agreement approved.
Bush said his policies in the Middle East have not always been popular and sometimes have fallen short of the administration's goals. "For example, the fight in Iraq has been longer and more costly than expected," he said.
Bush called the Israeli-Palestinian conflict the most "vexing" problem in the region - something that his administration has been seen as slow, at least in his early years as president, to aggressively mediate.
Still, he noted that he was the first U.S. president to call for a Palestinian state and said he sees progress toward reaching a two-state solution. After months of publicly insisting that an agreement between the two sides could be sealed by a year-end deadline, which was set by the two sides and Bush last November in Annapolis, Md., the Bush administration has conceded that it will hand the fragile, unfinished U.S.-backed peace effort to Obama.
Bush recalled the status of the Middle East talks when he came to office, following former President Bill Clinton's inability to forge an agreement at Camp David in 2000. The collapse of those talks gave way to the Al-Aqsa intifada, which broke out a couple of months after the Camp David peace summit in July 2000.
Bush said that in 2001, more than 500 Israelis and Palestinians were killed. He called the late Palestinian leader Yasser Arafat a "terrorist who stole from his people and walked away from peace." He also criticized former Israeli Prime Minister Ariel Sharon.
"Sharon was elected to fight terror and pursue a 'Greater Israel' policy that allowed for no territorial concessions," he said. "And neither side could envision a return to negotiations or the realistic possibility of a two-state solution."