President Bush said Saturday he planned to remind the world during a visit to the Korean Peninsula's demilitarized zone that North Korea seeks to "threaten freedom with weapons of mass destruction."

Bush, accompanied by his wife, Laura, walked across the South Lawn and boarded his Marine Corps helicopter to begin the journey Saturday morning.

In a radio address aired just after he left the White House for a six-day trip to South Korea, Japan and China, Bush did not back down from his recent characterization of North Korea as part of an "axis of evil," along with Iran and Iraq, that threatens U.S. security.

But he steered clear of that phrase, which alarmed European allies and fueled anti-American sentiment in Iran.

"I will visit South Korea and travel to the Demilitarized Zone, one of the most dangerous places on earth, where barbed wire marks a line dividing freedom and oppression," Bush said.

"The people of the south are now reaching out to the north in a spirit of friendship and reconciliation," Bush said. "I support these efforts. Yet I will remind the world that America will not allow North Korea and other dangerous regimes to threaten freedom with weapons of mass destruction."

Bush planned to lunch with some of the 38,000 American troops who help patrol the hostile border.

The president said he was also bearing a thank-you message for help from Asia following the terror attacks on New York and the Pentagon, and a progress report.

"The people of Tokyo, Seoul, and Beijing touched all our hearts in the days after September 11, with moving displays of sympathy and support in the wake of the terrorist attacks," Bush said. "Today, all three nations are supporting our fight against terrorism."

He also planned to give a boost to Japanese Prime Minister Junichiro Koizumi, whose approval ratings have sagged along with that nation's economy. Koizumi has offered a painful program of changes designed to right the Japanese economy and banking system.

"Today, Japan is in the midst of economic uncertainty and transition," Bush said. "But I have great confidence in Japan's future and in the unlimited potential of its people, and I'm confident that Japan will make the bold reforms needed to restore growth and opportunity, which will benefit the people of both our nations."

Bush also said he will prod the Chinese government to open up their markets to American agricultural products, and to embrace "the universal demands of human dignity, freedom of conscience and religion, and the rights and value of every life."