The 34-nation Summit of the Americas began Friday in Mar del Plata, Argentina, as demonstrators filled the streets of the town.

Leaders at Summit of Americas posing on first day of conference

The summit began with pomp and ceremony as the hemispheric leaders filed into an ornate auditorium. Meanwhile, the scene in the nearby streets was turning from order to chaos.

Before dawn, tens of thousands of demonstrators congregated for a day of protest. They marched peacefully down a main avenue, and filled the stands of a local football stadium for a rally in a wind-driven rain. But as the summit got underway, small groups began to move close to security barricades.

Protesters in Argentina at Summit of the Americas

They threw rocks and Molotov cocktails, broke shop windows, and burned American flags. Police clad in full riot gear responded by firing canisters of tear gas - the popping noise and acrid smoke filling the air.

But despite the trouble in the streets, the summit continued, though somewhat behind schedule, with participants sticking to their agenda and focusing largely on economic matters. The primary emphasis is on job creation as a means to prosperity for all in the hemisphere, but there are differences on the best way forward.

President Bush has been pushing trade and economic reform, and has met on the sidelines of the summit to discuss these and other issues with leaders from Central America and Andean countries, as well as Argentine President Nestor Kirchner.

President George W. Bush makes statement to reporters on opening day of Summit of the Americas

During a brief appearance with Mr. Kirchner, he referred to the massive security presence at the summit. "It's not easy to host all these countries. It's particularly not easy to host, perhaps, me."

This is the biggest security operation this resort city has ever seen - a situation that has become rather commonplace for any town chosen to host a multinational economic summit. But what was unusual about the gathering in Mar del Plata was one of the summit participants was playing a role in the demonstrations.

Venezuela's President Hugo Chavez, left, speaks to the crowd along with Argentine soccer star Diego Armando Maradona

Venezuela's President Hugo Chavez - a staunch critic of the Bush administration - addressed the stadium rally, lashing out at the Iraq war and vowing that the U.S plan for a free trade zone of the Americas will fail.

President Bush was asked what he will do when he comes face to face with Hugo Chavez at the summit. "Well, I will, of course, be polite. That's what the American people expect their President to do, is to be a polite person. And I will -- if I run across him, I will do just that," he said.

The two never spoke during the opening session. President Bush sat in the first row of the dais. President Chavez sat a few rows back.