Following up his surprise Thanksgiving trip to Iraq, President Bush is asking more Americans to volunteer to help military families.

President Bush says his secret, two-and-a-half hour visit to Baghdad's airport showed him U.S. troops in Iraq are committed to staying until the job is done.

"I'm pleased to report back from the frontlines that our troops are strong, morale is high and our military is confident we will prevail," he said.

In his weekly radio address, Mr. Bush said the men and women of the U.S. military are standing between the American people and the dangers of the world.

"In Afghanistan, Iraq and elsewhere our military is confronting the terrorist enemy, so we don't meet that enemy in our own country," president Bush said. "They are serving the cause of freedom. They are helping millions of people in newly liberated countries to build lives of dignity and hope. They are protecting the lives and security of the American people."

The president's political opponents are criticizing the surprise trip to Baghdad as a public relations stunt. They say the secrecy and brevity of the visit show White House policies have failed to restore security in Iraq.

President Bush told troops in Baghdad that they did not charge across the desert, depose Saddam Hussein and liberate the Iraqi people to be chased away by what he called a band of thugs and assassins.

More than 180 U.S. troops have been killed in Iraq since the president declared an end to major combat operations in May. In his radio address, Mr. Bush said the armed resistance to U.S. occupation is terrorism.

"It is the nature of terrorism that a small number of people can inflict such terrible grief," he said. "Every person who dies in the line of duty commands the special gratitude of the American people, and the military families that mourn can know this: Our nation will not forget their loved ones and the sacrifice they made to protect us all."

Mr. Bush called on Americans to volunteer to help the families of U.S. troops serving overseas, including through a program of his USA Freedom Corps that helps with home repair.

The president's surprise trip to Baghdad capped a week of good news for the White House, including strong economic numbers and Congressional passage of Medicare reform. Those changes to the health care system will be a big part of the president's domestic agenda during next year's re-election campaign.

Democrats used their weekly radio address to criticize the changes to Medicare. Tennessee Congressman John Tanner says the president's nearly $400 billion plan will not control rising prescription drug prices.

"The legislation that was passed in that controversial vote fails to deliver a meaningful, guaranteed drug benefit in Medicare and starts toward privatizing the program," said Congressman Tanner.

Democrats say allowing wealthier Americans to leave Medicare will reduce the pool of funds available to subsidize health care for poorer families.