FORT BRAGG, N.C. (AP) - President Bush on Tuesday appealed for the nation's patience for difficult and dangerous work ahead in Iraq, rejecting calls either for a timetable for withdrawal or sending more troops to battle the enemy.

"Sending more Americans would undermine our strategy of encouraging Iraqis to take the lead in this fight," Bush said. "And sending more Americans would suggest that we intend to stay forever."

He also said Iraqis must be reassured that "America will not leave before the job is done."

In an evening address from an Army base that has 9,300 troops in Iraq, Bush acknowledged the toll of the 27-month-old war. At the same time, he aimed to convince skeptical Americans that his "clear path forward" to victory needs only time - not any changes - to be successful.

(AP) President Bush waves as he exits Air Force One in the rain, at Pope Air Force Base in North... Full Image

"Like most Americans, I see the images of violence and bloodshed. Every picture is horrifying and the suffering is real," Bush said.

Bush said he knows Americans are questioning whether the heavy sacrifices in Iraq - more than 1,700 Americans dead - are worth it. "It is worth it, and it is vital to the future security of our country," he said.

He announced new steps the military is taking to prepare Iraqi security forces to take over the anti-insurgency battle: conducting operations together with Iraqi units, embedding U.S. transition teams inside Iraqi units and intensive management training inside the Iraqi Defense and Interior ministries.

"As the Iraqis stand up, we will stand down," he said.

Bush said the United States faces an enemy that has made Iraq the central front in the war on terror. Fighters have been captured from Saudi Arabia, Syria, Iran, Egypt, Sudan, Yemen, Libya and other nations, Bush said.

He described the insurgents in raw terms, calling them "ruthless killers" who commit "savage acts of violence" on innocents. He said the terrorists will not shake U.S. resolve in Iraq or elsewhere. "The terrorists do not understand America. The American people do not falter under threat - and we will not allow our future to be determined by car bombers and assassins."

"The only way our enemies can succeed is if we forget the lessons of Sept. 11 - if we abandon the Iraqi people to men like Zarqawi and if we yield the future of the Middle East to men like bin Laden." He referred to fugitive terror leaders Osama bin Laden, whom the United States holds responsible for the Sept. 11, 2001, terror attacks; and Abu Musab al-Zarqawi, a Jordanian responsible for scores of attacks in Iraq.

"For the sake of our nation's security, this will not happen on my watch," Bush said.

The speech was a tricky balancing act for the president, believed necessary by White House advisers who have seen dozens of deadly insurgent attacks each day eat into Americans' support for the war - and for the president - and increase discomfort among even Republicans on Capitol Hill.

Democrats and other critics said the country needs more specifics.

"We just don't have a clue what the criteria for success is," said Rep. John Murtha, D-Pa., a Vietnam combat veteran. "People are still willing to give the president time if he would just level with them. ... You can't just present a rosy scenario as if everything is going to be alright."

But Bush said that significant progress has been made, while much work remains. "The new Iraqi security forces are proving their courage every day," Bush said. He said more than 2,000 have been killed.

Bush said setting a timetable for withdrawing 135,000 American troops would be "a serious mistake" that could demoralize Iraqis and American troops and embolden the enemy. He also rejected calls by some to send more troops to Iraq, saying it could discourage Iraqis from moving as quickly as possible to take over the security of their country.

Instead, he argued for maintaining his present three-pronged strategy: hunting down insurgents, equipping Iraqi security forces to take over the anti-insurgency fight and helping Iraqi political leaders in the transition to a permanent democratic government.