The star of the 1969 road movie "Easy Rider" was in Cannes for the premiere of "The Big Fix" by Rebecca and Josh Tickell, the only feature documentary in the official selection at the Cannes film festival this year.
Fonda -- a keen environmentalist and co-producer of the film which centres on the explosion of the BP oil rig Deepwater Horizon, the ensuing spill and its consequences -- accused Washington of trying to gag reporting on the issue.
"I sent an email to President Obama saying, 'You are a f(expletive) traitor,' using those words... 'You're a traitor, you allowed foreign boots on our soil telling our military -- in this case the coastguard -- what they can and could not do, and telling us, the citizens of the United States, what we could or could not do'."
Fonda, who said he sent the email last week, appears in "The Big Fix" trying to get on to Louisiana beaches to assess the impact of the biggest oil spill in US history, only to be turned away by BP clean-up personnel.
Speaking at a press event at the American Pavilion to promote the film, Fonda denounced BP as "a bunch of Brits -- I thought we kicked them out a long time ago. They tried to get back in in 1812, but they didn't make it."
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