Leaders of 21 economies making up the Asia-Pacific Economic Cooperation group, or APEC, are in Vietnam for a week-long summit aimed at breaking a global trade impasse and improving regional security.

Summit organizers say they will try to focus on economic issues, but North Korea's possible nuclear threat will also be high on the agenda.

APEC representatives are expected to sign a so-called Hanoi Action Plan, restating their commitment to free and open trade and investment, that benefits both rich and developing countries.

Trade among APEC members accounts for nearly half of all global trade.

The summit begins Sunday. U.S. President George Bush, China's Hu Jintao, Russia's Vladimir Putin and Japan's Prime Minister Shinzo Abe are set to attend later in the week.

Mr. Bush is scheduled to meet one-on-one with several leaders before leaving for Singapore and Indonesia.

North Korea's underground nuclear test last month will be one of the topics discussed. Its neighbors and other states are concerned about economic disruptions if the nuclear crisis remains unresolved.

How to block terrorists' financial transactions is another security question before APEC, along with action against money laundering and other regional abuses of financial systems.