The group outside West Sussex council offices in Crawley want the government to let them return to Diego Garcia, which became a US airbase in the 1970s.
He asked Treasury Secretary Paulson to call the Russian authorities to let him fly his private jet over their airspace to return to the US and face the expanding crisis.
Mr Haass, who left the province to return to Washington on Wednesday afternoon, said the US Government would not let the actions of the terrorists go unchallenged.