A leftist economist who called for Ecuador to cut ties with international lenders appeared to have easily won the presidency of this poor, politically unstable Andean nation, strengthening South America's tilt to the left.

Partial returns from Sunday's voting showed that Rafael Correa -- who has worried Washington with calls to limit foreign debt payments -- would join left-leaning leaders in Bolivia, Brazil, Argentina, Chile and Venezuela, where he is friends with anti-U.S. President Hugo Chavez.

The returns showed Correa with as many as twice the votes recorded as for his banana tycoon rival, who claimed the polls were rigged.

Correa was a fresh face in a field of established politicians, and won a place in Sunday's runoff by pledging a "citizens' revolution" against Ecuador's discredited political system.

During the campaign, he called for Ecuador to cut ties with the World Bank and the International Monetary Fund. Correa, who has called President Bush "dimwitted," also wants to hold a referendum to rewrite the constitution to reduce the power of traditional parties and limit U.S. military activities in Ecuador.

"We receive this triumph with deep serenity and humility," the 43-year-old, who has an economics doctorate from the University of Illinois, told a news conference. "When we take office it will finally be the Ecuadorean people who are assuming power."

With 31 percent of the ballots counted, Correa had nearly 67 percent compared to 33 percent for Alvaro Noboa, Ecuador's Supreme Electoral Tribunal said before dawn Monday. Election officials said more returns were expected later Monday but that final results may not be known until Tuesday.

But Noboa, a Bible-toting billionaire who counts the Kennedys and Rockefellers among his friends, declined to concede defeat, saying he would wait for the final vote results.

"There has been a scenario in which they are preparing to commit fraud," Noboa told dozens of his supporters in the coastal city of Guayaquil. He said he instructed his campaign chiefs "to go to the Supreme Electoral Tribunal and demand that they open the ballot boxes to count vote for vote so there can be no doubt."

Ecuador has had eight presidents since 1996, including three who were driven from office by street protests.

Correa pledged to construct 100,000 low-cost homes and copied Noboa's promise to double a $36 "poverty bonus" that 1.2 million poor Ecuadoreans receive each month.

Correa began his campaign identifying with Chavez, but backpedaled when he feared the comparison was hurting him in the polls. That appeared to change somewhat Sunday night.

"Hopefully, we will get much, much closer to Chavez," he told Channel 8 television in an interview. "Chavez is my personal friend, but in my house, my friends aren't in charge, I am. And in Ecuador, it will be Ecuadoreans in charge."

He said he would not rule out also seeking stronger ties to other more moderate leftist presidents like Michelle Bachelet in Chile, Nestor Kirchner in Argentina and Luiz Ignacio Lula da Silva in Brazil, and with Washington, if President Bush makes it worthwhile for Ecuador.

Correa stood firm, however, on not signing a free-trade deal with the United States, "because, among other things, it would destroy our agriculture, cattle and poultry" industries.

At his first news conference following the election, Correa said Ecuador could rejoin the Organization of the Petroleum Exporting Countries, or OPEC.

"If it is possible we will rejoin OPEC," he said. Ecuador, which produces some 535,000 barrels of oil a day, left OPEC in 1993.

He also announced that leftist economists Ricardo Patino and Alberto Acosta, whom he had mentioned earlier as possible Cabinet ministers, would be appointed to head the ministries of economy and energy.

Correa was favored to win the first round but came in second to Noboa in the field of 13 after his comments on Bush and threat to reduce payments on Ecuador's $16.1 billion foreign debt rattled investors.

Prior to the second round of voting, he softened his radical rhetoric and began to make populist promises of his own.

Correa served just 106 days last year as finance minister under interim President Alfredo Palacio, who replaced Lucio Gutierrez in the midst of street protests in April 2005.

Noboa, who was seeking the presidency for the third time, had run an old-fashioned populist campaign, crisscrossing Ecuador handing out computers, medicine and money.