Venezuelan leader Hugo Chavez (search), emboldened by thousands of anti-American protesters, is getting a rare chance to stand up to his adversary, George W. Bush (search), with promises to keep the president from reviving talks on a free trade area stretching from Alaska to Argentina.

The two men were to arrive in Argentina (search) for the fourth Americas summit on Thursday, the same day Venezuela is staging a mock U.S. invasion of its own territory. The event is the latest exercise intended to prepare soldiers and civil. officials deny any such plan, but Chavez says it's best to be ready -- just in case.

With tensions rising between the two nations, Chavez and Bush will likely see each other Friday at the summit's inauguration -- after Chavez addresses a rally of mostly anti-Bush protesters. The two leaders are not scheduled to meet one-on-one, but they will both be taking part in the same summit sessions.

Chavez has joked about whether Bush is afraid of him, saying he might sneak up and scare Bush at the summit.

Bush has brushed aside Chavez's attempts to turn the summit into a showdown, saying he is focused on announcing job creation programs and promoting free trade in the region.

"The purpose of the summit is for the democratically elected leaders to get together and reaffirm the fact that there is really a shared vision for the hemisphere," National Security Adviser Stephen Hadley said in a pre-summit briefing in Washington.

There are signs the U.S. may be winning over supporters for the proposed Free Trade Area of the Americas (search), the summit's main sticking point. A high-ranking Brazilian official who said he wasn't authorized to give his name told The Associated Press that 28 of the 34 countries participating in the summit had agreed talks should begin as early as April.

Negotiators missed a January 2005 deadline for wrapping up talks on the agreement.

The region has been divided over the FTAA, as Venezuela uses the issue to try to recruit supporters of its own so-called socialist "revolution."

Chavez has used Venezuela's oil wealth to push for regional solidarity, offering fuel with preferential financing to various Caribbean and Latin American countries.

He also bought $950 million this year in Argentine bonds, saying it was a step toward creating a so-called Bank of the South to help provide financing to the region.

Chavez is expected to push that banking initiative at the two-day summit.

Some in the Bush administration have expressed concern about Venezuela's desire to build a nuclear power reactor. And, after Chavez said he might share his U.S.-made F-16 fighter jets with Cuba and China, U.S. Ambassador to Venezuela William Brownfield said that decision would need U.S. approval.

Still, those issues are unlikely to come up at the summit.

Instead, Bush will be holding bilateral meetings on everything from drug trafficking in Colombia to free trade.

Cuba (search), Venezuela's closest ally, is banned from participating in the summit. But Cuban Foreign Minister Ricardo Alarcon showed up in Mar del Plata anyway.

He mocked the process, telling Associated Press Television News: "They are going to take a good photo with Bush, have lunch, eat dinner, and gab some more. What is happening over there is a plan that does no good for the people of the Americas."

As hundreds more protesters began pouring into the resort for Friday's protests, police with riot shields redoubled security. Navy ships patrolled offshore as helicopters clattered over the luxury hotel where leaders will meet.

"We're going to say 'No to Bush' and 'No to FTAA,"' said Argentine labor leader Juan Gonzalez. "We don't have any confidence in anything he might propose here, whatever it is will only prolong hunger, poverty and death in Latin America."

Many protesters rallied in Buenos Aires before boarding buses and cars bound for Mar del Plata (search). Demonstrators opposed to everything from the war in Iraq to free trade toted backpacks and sleeping bags, some coming from as far as Argentina's northernmost border with Bolivia.

Santiago Zamora, a 30-year-old biology student from northern Argentina, sported a red Che Guevara (search) shirt.

"We are going to fight against all forms of imperialism," Zamora said, voicing complaints against free-market programs some here blame for enslaving poor Latin American countries.