Evo Morales, the Bolivian president, has reached a deal with opposition politicians to hold a referendum on a new constitution after agreeing to limit himself to running for only one more term in office.

The agreement was reached late on Monday after Morales led a march of more than 100,000 of his supporters on congress.

"Four political parties agreed to make the ratification of the constitution possible, the referendum to approve the constitutional draft will take place on January 25," Morales told thousands of cheering supporters in the capital, La Paz.

On Tuesday, Morales remained camped outside the Bolivian congress with protesters in an attempt to pressure legislators to pass the agreement.

The new constitution, which would give more power to Bolivia's indigenous majority, has been the subject of violent protests by the country's opposition.

Morales had joined the last stage of the week-long 200km march in favour of the constitution by peasant farmers, activists and miners as it entered La Paz.

The new constitution would allow him to seek re-election in 2009 but forbids him from seeking a third term in 2014.

Constitution unrest

Violence broke out over the proposals last month, leaving 19 people dead and martial law imposed by the goverment in one province.

Bolivia's constitutional court had rejected a decree Morales had issued calling for a December referendum on his new constitution, saying such a move could only be scheduled by congress.

The move led to the protests by rural workers and union members backing Morales.

The proposed constitution would redistribute land to Bolivia's poor indigenous communities, but has met fierce resistance from provinces in the east of the country, who say it overlooks their demands for greater regional autonomy.