WikiLeaks has brokered an offer of political asylum for United States intelligence whistle-blower Edward Snowden and is assisting his travel from Hong Kong via Moscow to another as yet unidentified country.

WikiLeaks publisher Julian Assange on Sunday confirmed his organisation's involvement in Mr Snowden's sudden departure from Hong Kong ahead of US government efforts to secure his extradition on espionage and other charges arising from the leak of top secret US National Security Agency surveillance programs.

"Mr Snowden is flying in an Aeroflot aircraft over Russian airspace, accompanied by WikiLeaks legal advisers," Mr Assange said.

"He is expected to land in Moscow at 5pm, local time (11pm, 23 June, Eastern Australian Standard Time) and will be met by diplomats from the country that will be his ultimate destination. Diplomats from that country will accompany him on a further flight to his destination."