COBIJA, Bolivia -- For two hours, President Evo Morales huddled in this jungle city with a dozen area mayors as they pitched public-works projects -- to be financed directly by Venezuelan President Hugo Chávez.

The Venezuelan and Cuban ambassadors to Bolivia flew here aboard the presidential jet to join the talks. The public was kept out.

After the money was divided up, Morales invited the media in and offered the mayors, one by one, a handshake and a Venezuelan embassy check for up to $150,000. In all, Venezuela gave about $1.5 million that day last November.

"I admire the Venezuelan government for showing this solidarity, " said a beaming Walter Valverde, mayor of the town of Puerto Rico, holding a $28,917 check to build a new hospital.

Flush with oil profits, Chávez is making an unprecedented effort to win the hearts and minds of citizens from Buenos Aires to Boston as he seeks to export socialism and challenge the United States' traditional role as the region's dominant player.

With Chávez's multibillion-dollar gusher of aid, Bolivia is building new schools. Argentina paid off its debt to the International Monetary Fund. Caribbean nations are receiving subsidized oil. Even the U.S. poor and American Indians have received discounted heating oil.

With Cuba's Fidel Castro sidelined by illness, Chávez, 53, has emerged as the region's most influential leader. Many in power have turned a blind eye to his foreign activism and increasingly authoritarian rule at home, much to the dismay of the United States and several Latin American nations.

But now he has reached a difficult juncture. His stunning defeat in a Dec. 2 vote on constitutional reforms shattered his image of invincibility. Domestic opponents are gathering steam, and some of Chávez's neighbors are voicing increased concern.

Observers throughout the region are scrutinizing Chávez's every move to determine how far he will push his vision of "21st century socialism." The concept is still fuzzy, but it is clearly a hard-left ideology that gives the state a much stronger role in the economy -- or maybe even a communist system like Cuba's.

The betting is that Chávez will continue to use his petrodollars to aggressively advance his cause, said Daniel Hellinger, a professor at Webster University outside St. Louis, who closely follows Venezuela.

"You can't just write this guy off, " Hellinger said. "He's impatient and intemperate. He has an outsized ambition and an outsized ego. . . . Chávez has a deep sense of mission, which is both dangerous and admirable. He sees himself as transforming Venezuela into a more modern and just society."

VENEZUELAN FOCUS

After grudgingly accepting his Dec. 2 defeat on changes that would have allowed him to seek reelection indefinitely and given him vast new powers, Chávez promised to move more cautiously, saying that his revolution's "main motor seized up, so we'll have to go by donkey instead."

But he insisted that his general direction was correct, and in a major speech two weeks ago, he called on hard-core supporters to push for removal of the constitutional barrier to his reelection. There seemed no doubt that they would oblige as they chanted an old Cuban slogan: "The people, united, can never be defeated."

Chávez also recently nationalized several foreign-owned mining operations and threatened to seize banks and even asphalt plants, which he accused of favoring exports over the domestic market.