Colombia's leftist rebel group FARC has said it is putting peace talks in Cuba on pause to examine a government proposal that any peace agreement must be submitted to a national referendum.

"In light of this new circumstance, the FARC's peace delegation has decided to make a pause in the talks to centre itself exclusively on the implications of the government proposal," FARC negotiator Pablo Catatumbo said on Friday, reading out a statement in Havana.

President Juan Manuel Santos announced on Thursday that he was submitting legislation to Congress that would require a referendum to be held on any peace agreement reached with the leftist rebels.

The latest FARC announcement was the first interruption in talks that began in November.

Al Jazeera's Alessandro Rampietti, reporting from Bogota, said the statement was not an end but an obstacle to the peace talks.

"FARC was really careful of the wording of the statement and it said that it called a 'pause'. However it was not certain how long this suspension will go on," he said.

It came after the rebels on Tuesday for the first time accepted partial responsibility for the thousands of victims of the country’s nearly 50-year-old conflict while suggesting creation of a truth commission.

Even as the FARC has been severely weakened in the last 10 years by a heavy military offensive, it remains a formidable threat to the government.

Formed in the 1960s, it is the oldest active guerrilla group in the Western Hemisphere and it is believed to have about 8,000 armed fighters.

A government commission last month estimated that about 220,000 people have lost their lives in Latin America's oldest armed conflict. Other estimates rise as high as 600,000.

Source: Al Jazeera and agencies