By Rosa Tania Valdes

HAVANA (Reuters) - Colombia's Marxist FARC rebels charged on Friday that the hostile attitude of President Juan Manuel Santos threatened peace negotiations under way in Havana and urged him to salvage the talks, in their harshest criticisms since talks began three months ago.

Santos infuriated the rebels earlier this week when he said they should be responsible for compensating the of thousands of farmers who were forced to flee their lands during the region's longest and only remaining guerilla war.

The FARC considers itself the representative of Colombia's rural poor in their conflicts with big landlords and foreign mining and oil companies.

"It is true that at the negotiating table there has been important progress made, but the official attitudes ... threaten to sink them in a swamp. Let's get it out of there now, Santos," said a statement by FARC leader Rodrigo Londono, alias Timoleon Jimenez, distributed in Havana as the talks resumed. "Let's save it," he added.

Earlier this week the FARC also branded the Santos government as a "Pinocchio" for promising to set aside a large swath of land for the dispossessed.

Responding to the rebel statement, Colombian Interior Minister Fernando Carrillo told journalists in Bogota, "It's in their hands to pull it out of the swamp. Let them stop kidnapping and attacking Colombians."

Throughout the negotiations both parties have questioned the other's sincerity and condemned bombings, kidnappings and military actions that have increased in intensity in recent weeks.

At the same time the government, FARC and their Cuban and Norwegian facilitators have said progress was being made at the negotiating table, without providing any details.

The parties are trying to end a war that dates to the FARC's formation in 1964 as a communist agrarian reform movement fighting Colombia's long history of social inequality and the concentration of land in the hands of a few.

Tens of thousands of people have died and millions more have been displaced in the war, Latin America's longest running insurgency and a vestige of the Cold War.

The talks are built on a five-point agenda addressing the issues that provoked and prolonged the war, starting with land reform and rural development.

The FARC has proposed giving a broad swath of Colombia to the poor, but the government has said land will not be taken from private owners.

Remaining issues include FARC's future political participation, ending the conflict, compensation for victims of the war, and drug trafficking, which has helped fund the group for years.

(Reporting by Marc Frank; Editing by David Adams and Vicki Allen)