The Bolivian vice president has signed into law a controversial constitutional amendment to allow President Evo Morales to run for a third term.

Vice President Alvaro Garcia Linera signed the law on Monday in the presence of parliamentarians, members of the armed forces and representatives from Morales' party.

"President Evo Morales is constitutionally permitted to run for re-election in 2015," said Linera after signing the documents.

The Bolivian constitution says a president can only serve two terms, but last month Bolivia's Supreme Court ruled that Morales' first term did not count because the constitution was changed in his first four years.

Opposition leaders have said they will try to get the ruling overturned, despite Morales not officially stating whether he will run for a third term.

Morales became Bolivia's first indigenous president in 2006 and was re-elected in 2009 after amending the constitution.

His current term runs to 2015.

Morales, 53, would get 41 percent of the vote in a national election, according to a poll released last month. His closest rival, Samuel Doria Medina, would get 17 percent.

Morales is currently visiting the US, where he is to meet former president Jimmy Carter over the issue of sea access for the landlocked South American country.