La Paz - Following a months-long political struggle, leftist Bolivian President Evo Morales on Tuesday obtained the necessary majority in Congress to call a referendum on a controversial proposal for a new constitution.

Voters will weigh in on the proposal in a January 25 referendum. The opposition backed Morales' proposal, following an agreement on the previous day that was pending an official vote in Congress. Congress debated almost without interruption for 18 hours, while Morales himself and many thousands of supporters waited for the results outside the building.

The president could not contain his tears upon hearing the result, while thousands of peasants, social activists and indigenous people who had accompanied him celebrated their triumph.

"We have the law that the Bolivian people demanded so much," said Bolivian Vice President Alvaro Garcia Linera, as president of Congress.

Over the previous hours, Morales had has to calm down impatient supporters.

Rural Development Minister Carlos Romero said on Monday the agreement moves up the next general election by one year, to January 2009, which President Evo Morales would contest for his second and final term.

"We have worked day and night to reach an accord," Romero said. "President Morales even had to renounce the possibility of a second re-election after the constitution is approved."

The draft charter enshrines many of the president's reforms that favour the indigenous majority and allow state control over key sectors of the economy, which have angered the country's wealthier sectors to the point of violent clashes last month that took 19 lives.

Morales, a former coca farmer who became the country's first ethnically indigenous president, has polarized the country by trying to spread the wealth from the resource-rich eastern plains to the poor western Andean region.

After a court struck down his call for a December referendum, saying only the congress had to power to call one, Morales led a demonstration of 50,000 indigenous peasants and leftist activists into the capital to pressure the congressional opposition.

Fearing further violence, opposition leaders agreed to the plebiscite, after first extracting a pledge from Morales that he would not seek re-election in 2014, if he wins a second term. (dpa)