Colombian President Juan Manuel Santos said Friday that he hoped the war with Marxist FARC rebels would end "very soon" after further progress this week on peace talks in Cuba.

"We hope that very soon the issue related to the definitive ceasefire between FARC and the government will be resolved," Santos told reporters during a visit to London.

This would mean "the end of the armed conflict", he said, adding that it would be the "end of FARC as an armed group".

"That is is very important news, and I hope that we will get there very soon," he said.

He was speaking after agreement the day before in Havana that the peace deal with the Revolutionary Armed Forces of Colombia (FARC) would be recognised in the Colombian constitution.

Santos has previously been reticent about imposing any deadlines on a deal after an earlier one came and went.

Interior Minister Juan Fernando Cristo said on Wednesday that peace talks were in the "home stretch" and said Colombia plans to hold a referendum on the deal by September.

The conflict with FARC is Latin America's longest running civil war, which has drawn in several leftist rebel groups, right-wing paramilitaries and drug gangs.

It has left 260,000 people dead and 45,000 missing, while another 6.6 million have been uprooted. Human rights groups say atrocities have been committed on all sides.