Colombia's leftist rebel movement has said that it has been holding a former US serviceman for nearly a month and offered to release him to a humanitarian commission.

The Revolutionary Armed Forces of Colombia (FARC) said in a statement on Saturday on its website that they have "made the political decision to release him as a gesture in the context of the peace talks" with the Colombian government.

Kevin Scott Sutay, a veteran of the Afghan war, was seized on June 20, said the rebels, who are engaged in peace talks with the government aimed at ending Colombia's nearly half-century-old conflict.

The rebels said that Sutay identified himself as a 2010-11 veteran of the Afghan war who was an anti-mining and explosives specialist in the US Navy until March of this year.

The FARC did not explain the circumstances of Sutay's "capture" but said it proved that the US has "mercenaries in the country".

The rebels said Sutay had been in the nearby town of San Jose de Guaviare, where a Colombian military base is located.

Civilian contractors

The US military has long assisted Colombia's armed forces and at any given time has dozens of uniformed personnel as well as civilian contractors in the country.

Three US army contractors held by the FARC for more than six years were rescued in 2008 along with former presidential candidate Ingrid Betancourt and a group of Colombian soldiers and police.

Formed in 1964, the FARC by its Spanish acronym, is the country's largest armed group, with an estimated 8,000 fighters.

Peace talks between the rebels and the government opened in November last year in the Cuban capital Havana, in the fourth attempt since the 1980s to bring peace to the Latin American country.

The war has ravaged Colombia for nearly fifty years and has left 600,000 dead, more than 3.7 million displaced and 15,000 missing.

Source: Agencies