Asia-Pacific leaders opened their annual summit Friday in which they were expected to launch a bid to revive stalled global free trade talks and pledge unity in combating a potential bird flu pandemic and international terrorism. Outside the venue, riot police were using high-powered water hoses to hold off some 4,000 demonstrators. The demonstrators marched on the summit in the port city of Busan, where leaders gathered from the 21-member Asia Pacific Economic Cooperation forum, including US President George W. Bush, Chinese President Hu Jintao, Japanese Prime Minister Junichiro Koizumi and Russian President Vladimir Putin. When they reached a blockade of shipping containers placed by police in a road near the convention center, some of the protesters began banging on the containers and demanding to pass. Police ordered them to stop, and when they refused to comply, the police turned water hoses against the crowd to try to disperse them. A group of dozens of protesters threw rocks and other items at black-clad security forces armed with riot shields and batons. Some also set fire to some debris, sending black smoke into the air. The clashes occurred about 500 meters across a river from the meeting venue. As they marched toward the site in which the summit was taking place, the protesters chanted slogans and carried signs reading, among other things, "Get rid of APEC" and "Let's get Bush." They were led by thousands of farmers, who have been angrily outspoken in South Korea over plans to liberalize the country's rice market. Tens of thousands of police and military forces have been deployed in the city in order to prevent terror attacks and to keep protesters away from summit venues. The leaders are set to endorse a statement agreed upon earlier by APEC ministers that aimed at fostering progress in World Trade Organization talks set for next month in Hong Kong. That statement acknowledged "considerable divergences" and said "a clear roadmap" must be established if the current so-called Doha round of WTO talks was to succeed. Earlier Friday, the presidents of Chile and Mexico defended bilateral and regional free trade agreements as good for their economies, but emphasized that the ultimate goal remained a strong WTO-based multilateral trading system. China and Chile signed a free-trade agreement on APEC's sidelines - the first between the Asian giant and a Latin American country. "It is essential that the leaders be able to put all of our political will and to instruct the negotiators that it is necessary to succeed," Chilean President Ricardo Lagos told a chief executives' gathering alongside the APEC summit. Mexican President Vicente Fox told the executives that APEC must "come up with a very solid, strong voice" ahead of the WTO's Hong Kong meeting. But there was also pessimism about what can be accomplished. "It's not being melodramatic to say that unless there is a very significant shift in the attitude of some countries, we are not going to have a successful Doha trade round," Australian Prime Minister John Howard said. He named the European Union and Japan as holdouts on lowering agricultural subsidies. In their own statement to be endorsed as the "Busan Declaration," the leaders will give their support to free trade and also express strong concern about the threats of terrorism and bird flu, according to a draft of the document seen by The Associated Press. "Terrorism remains a menacing threat to our world and we condemned terrorist acts that not only took thousands of lives but have also been aiming to destabilize the security of the region," the draft states. Concerns about a possible human pandemic spawned by bird flu have grown in recent days, with China announcing its first human cases and the first deaths. Bush is expected to make bird flu a major focus, and APEC leaders are set to agree to boost their preparedness against a possible outbreak. Howard urged countries to put aside "national pride or self-consciousness" and be open about reporting outbreaks. "The last thing that any nation can afford, not only in its own interests but in the interests of fellow members of the world community, is to in any way hide or cover up the onset of the signs of an outbreak of something that could turn into a pandemic," Howard said at the executives' forum. Alongside the forum, Bush met with Southeast Asian leaders to underscore US interests in the region - one of the battlegrounds in the fight against terrorists - and to urge them to exert their influence on Myanmar's military junta. He also met with Russian president Vladimir Putin. Amid a diplomatic row over allegations that Japan was glorifying its colonial past, Roh will briefly meet Friday with Japanese leader Koizumi, who has reignited anger in South Korea and China by again visiting a shrine honoring convicted war criminals among other war dead. The summit ends Saturday.