The group, Free West Papua Campaign, says the United States office of Homeland Security stopped West Papuan independence activist Benny Wenda from boarding a flight from London to Los Angeles.
The group says check-in staff found an alert on Mr Wenda's passport and he was then questioned by a US official at Heathrow airport.
It says Mr Wenda told the official he's a Human Rights campaigner from West Papua who was exiled, and is now campaigning for West Papua.
After making phone calls the US official told Mr Wenda that his US visa had been revoked, but declined to say why. He told Mr Wenda to contact the US
Benny Wenda was issued a ten year US business visa in October 2014, and has already made one visit to US Congress staff on Capitol Hill in Washington.
He was set to embark on a speaker tour of California and Hawai'i at the invitation of US groups supporting the Free West Papua Campaign.
Mr Wenda says concern is growing from people, politicians and UN officials in the US about the ongoing violence in West Papua.
He says hopes US officials respond to his situation soon so he can join the tour.
The Free West Papua Campaign says it's not the first time Mr Wenda has been prevented from travelling to the US, in 2005 and 2013 he had visa applications refused and then went on to successfully apply for his current ten year business visa.
It says its keen to know why Mr Wenda's legitimate right to free speech in the US has been quashed and is working to try and get his visa reinstated.