Gen. Peter Pace, chairman of the Joint Chiefs of Staff, took the administration's baton Thursday, making the case that "relentless progress" is happening on the ground in Iraq.

Speaking at the National Defense University at Fort McNair, Pace explained that the United States would not be better off by vacating Iraq before its mission is complete.

"There is no option other than victory," he said. "You need to get out and read what our enemies have said ... Their goal is to destroy our way of life."

Pace acknowledged that the military hasn't done a good enough job of explaining to the American people what is going on in Iraq. He warned that battling terrorism will take a long time.

Asked after his speech why a gap exists between what commanders and administration are saying and what the media and American public are perceiving, Pace said the military has not articulate its progress well enough.

"It's incumbent not only on folks like me in Washington, but also on lieutenant colonels and colonels and captains and lieutenants and lance corporals and corporals when they come home, we should be encouraging them inside their local communities to take the opportunity to talk to the local newspapers, to the local chamber of commerce; just to be able to answer our fellow citizens' questions," he said.

Pace spoke one day after President Bush used a speech at the U.S. Naval Academy in Annapolis, Md., to spell out what he called his strategy for victory in Iraq. The president told Midshipmen at the Naval Academy that he won't set a timetable or bow to political pressure for an early withdrawal.

At the same time, he suggested that some U.S. troops could be withdrawn next year because Iraqi troops are being quickly trained. He added that Iraqi troops don't have to be trained to be of equal caliber force to coalition troops.

"Not every Iraqi unit has to meet this level of capability in order for the Iraqi security forces to take the lead in the fight against the enemy. As a matter of fact, there are some battalions from NATO militaries that would not be able to meet this standard. The facts are that Iraqi units are growing more independent and more capable," he said.

The White House said the response to the president's strategy for victory has been largely positive from Republicans and some Democrats, though support for Bush is largely breaking down along party lines.

Democrats say Bush didn't show them any light at the end of the tunnel. And Rep. John Murtha, D-Pa., fired another shot at the administration, saying the war in Iraq is hurting the military's ability to meet future threats.

For instance, he said, the Pennsylvania National Guard is "stretched so thin" that it won't be able to deploy fully equipped units to Iraq when it goes next year.

The Army is "broken, worn out" and "living hand to mouth," Murtha told a business group in Pennsylvania on Wednesday. He predicted that the troops would be pulled out in the next year.

Murtha's criticism stings the administration because the Vietnam war veteran spent 37 years in the Marines and his opinion on military matters carries weight. So when Murtha said the Army is now living from hand to mouth, the White House aimed to knock it down quickly. Administration officials pointed out that the Pentagon disagrees and assured Congress earlier this year that U.S. forces are fully equipped and prepared.

Meanwhile, a day after laying out his strategy for victory in Iraq, Bush invited Sen. John Kerry, D-Mass., to the White House and gave the Democrat a stage from which to challenge him. Kerry said the United States doesn't need 160,000 troops in Iraq and that the president needs to bring some of them home.

"I'm not asking even for the specific timetable of withdrawal. I'm asking for a specific timetable of transfer of authority, of transfer of responsibility, of the shift and the setting of the benchmark specifically that allow us to bring our troops home," Kerry said.

Kerry said he wants 20,000 soldiers home before Christmas and substantially more to come home next year.

White House officials say they won't bow to political pressure to bring the troops home, but that conditions will probably be right for a partial withdrawal next year.

"We fully expect, as the Pentagon has indicated, that we're going to be able to reduce some of the troop levels that we increased heading into the elections after the elections take place. And then, from there, I mean, I think some have talked about how next year could be a period of significant transition," said White House spokesman Scott McClellan.

McClellan said the key to all of that is the degree to which Iraqi troops are trained. On Wednesday, the president said that training is going well. Bush also urged patience, claimed steady progress and vowed to accept nothing less than "complete victory."

"We will continue to shift from providing security and conducting operations against the enemy nationwide to conducting more specialized operations targeted at the most dangerous terrorists," Bush said. "We will increasingly move out of Iraqi cities, reduce the number of bases from which we operate and conduct fewer patrols and convoys."

Bush also emphasized recent progress in the training of Iraqi security forces, saying they now control several sections of Iraq, including large portions of Baghdad.

"Victory will come when the terrorists and Saddamists can no longer threaten Iraq's democracy, when the Iraqi security forces can provide for the safety of their own citizens, and when Iraq is not a safe haven for terrorists to plot new attacks on our nation," he said.

In noting that U.S. forces have begun turning over control of military bases to the Iraqis, Bush singled out the Nov. 22 handover of a base near Tikrit that includes one of Saddam Hussein's former palace complexes. Bush said it had served as a U.S. military headquarters "in one of Iraq's most dangerous regions."

It's not clear that terrorists have used Iraq as a haven to plot attacks on the United States, but Bush's remark suggested a like-mindedness between terrorists in Iraq now and those who planned the 2001 suicide hijack attacks. The two "share the same ideology," Bush said, of seeking to "sow anger and hatred and despair."

James Jeffrey, the Iraq coordinator at the State Department, said that Iraqi security units were getting better, in some cases strengthened by the absorption of former troops of deposed President Saddam Hussein. But speaking at the Washington Institute for Near East Policy, he said Iraqi forces were mostly light infantry and needed more armor and declined to say when he thought U.S. troops could quit the country.

While stoutly defending his war strategy, Bush also acknowledged some setbacks and cautioned that the months ahead would be difficult. He noted that the Iraqi security force originally created to fight the insurgents "proved to be no match" for the enemy, and that some early training for Iraqi police was inadequate.

"Their performance is still uneven in some areas," Bush said, referring generally to Iraqi security forces.

Bush's speech was the first in a series of planned presidential addresses aimed at shoring up public support for a war that has lasted much longer and caused more U.S. casualties than the administration originally expected.

FOX News' Bret Baier and Wendell Goler and The Associated Press contributed to this report.