US intelligence officials have said computer files seized from a Colombian rebel leader's laptop computer are authentic and show strong ties between Farc and Hugo Chavez, Venezuela's president.
The files describe meetings between rebel leaders and Venezuelan officials, including Chavez, a report in The Wall Street Journal said on Friday.
One intelligence official said the analysis "reinforces the US government's strong position that Chavez is attempting in various ways to project his influence throughout the region".
"That influence in some ways could be construed as destabilising," he said.
The Reuters news agency reported another US official as saying the files were a public relations victory for Colombia, which is battling Farc fighters.
"The involvement does seem to extend fairly high up in the Venezuelan government. This isn't a bunch of local yokels on the border doing their own thing," the official said.
Offer of arms
Chavez, whose sympathies for Farc are well known, contends that the files have been faked by the Colombian government.
Colombia has said the files, which were seized in an attack on Farc fighters in March, show Chavez offered financial support to the group.
The Wall Street Journal report said the files also indicated Venezuela offered to arm Farc fighters, possibly with rocket-propelled grenades and ground-to-air missiles, and said Venezuela offered Farc the use of a port to receive arms shipments.
Bernardo Alvarez, Venezuela's ambassador to the US, told the newspaper on Wednesday, that the computer files were "false and an attempt to discredit the Venezuelan government".
The March attack by Colombia on a Farc base in Ecuador killed a senior Farc leader, but also increased tensions in the region and prompted Chavez to mobilise Venezuela's military along the country's border with Colombia.