Asia-Pacific leaders are to pledge to tackle a deadlock in global trade talks at a key regional summit in Vietnam.
President Bush is likely to hold talks with other leaders on North Korea
In a draft statement circulated before the Asia-Pacific Economic Co-operation (Apec) forum, the leaders say they will take the lead by making concessions.
World Trade Organization (WTO) talks collapsed in July after countries failed to reach agreement on subsidies.
President Bush has been holding talks with regional leaders to boost support for sanctions against North Korea.
Over a bilateral breakfast meeting, he urged South Korean President Roh Moo-hyun to implement the sanctions and also support the US-led Proliferation Security Initiative (PSI), a voluntary programme designed to prevent the trafficking of material for weapons of mass destruction.
Mr Roh said he supported the principles of the PSI but left the level of Seoul's compliance unclear, saying he would not take part in the "full scope" of the initiative.
In a lunchtime meeting between Mr Bush and Japanese Prime Minister Shinzo Abe, the two leaders agreed to pursue a ballistic missile defence programme against the threat from North Korea.
Mr Bush will see Chinese counterpart Hu Jintao and Russian President Vladimir Putin on Sunday.
Mr Bush may also use the summit to try to gather support for a free trade zone between the organisation's 21 members.
Correspondents say the proposal is seen as an insurance policy in case efforts to revive world trade talks fail.
The global WTO talks were meant to boost free trade for the benefit of developing countries.
But an inability by the US and Europe to agree over how to reduce agricultural subsidies caused the talks to stall in the so-called Doha round.
According to the draft statement, the 21 Apec leaders will say: "We are ready to break the current deadlock - each of us is committed to move beyond our current positions in key areas of the Doha round."
This will mean opening up agriculture markets and "making deeper reductions in trade-distorting farm support by major players", it says.
The leaders will pledge to "remain personally involved" in pushing negotiations forward and trying to secure a breakthrough.
Apec's trade and foreign ministers agreed to press their leaders to issue a statement on trade in the course of the two-day conference.
"Only an ambitious Doha agreement with real market access can achieve the economic growth and development goals that this world has set," Mr Bush said in Singapore before heading to Hanoi.
The forum in the Vietnamese capital is also expected to focus on economic security threats.
Indonesian President Susilo Bambang Yudhoyono told business leaders on Friday that economic security must be on every country's agenda.
This would ensure they could work together against such threats as terrorism, flu pandemics and natural disasters, he said.
Speaking after his arrival on Friday, Mr Bush said he felt amazed to be in Vietnam given the two countries' difficult history.
Following talks with Australian Prime Minister John Howard, Mr Bush said he would consult Australia over any repositioning of troops in Iraq.
The two leaders also discussed climate change. Mr Howard had promised to seek support for alternatives to the Kyoto Protocol.
Meanwhile New Zealand Prime Minister Helen Clark urged Apec leaders to include climate change on their agenda, warning of "dire" consequences if action was delayed.