President Bush says a formal peace treaty ending the 1950-1953 Korean War can be achieved only after North Korea "verifiably" ends its nuclear weapons program.

Mr. Bush made the comment after talks with his South Korean counterpart, Roh Moo-hyun, on the sidelines of a summit of Asia-Pacific leaders in Sydney, Australia. The focus of their talks was North Korea, which agreed in February to end its nuclear program in exchange for political concessions and fuel aid.

Also Friday, Mr. Bush met with Russian President Vladimir Putin.

Earlier, in a speech to business leaders, President Bush urged Pacific rim nations to take the lead in world trade talks, and band together to fight global warming and combat terrorism.

He also said the United States and other countries must encourage more political openness in China.

Mr. Bush condemned the Burmese government's crackdown on pro-democracy activists, and called for free elections in Thailand.

After a lunch meeting with Southeast Asian leaders, Mr. Bush invited them to visit him in the southern U.S. state of Texas, and said he would soon be announcing an ambassador to the Association of Southeast Asia Nations.

Mr. Bush is among 21 leaders taking part in the Asia-Pacific Economic Cooperation summit. At APEC sessions beginning Saturday, the leaders are expected to call for a resumption of stalled global trade talks, and push for action on climate change.

Some information for this report was provided by AP