Guyana achieved independence from the United Kingdom as a dominion on 26 May 1966 and became a republic on 23 February 1970, remaining a member of the Commonwealth. Shortly after independence, Venezuela began to take diplomatic, economic and military action against Guyana in order to enforce its territorial claim to the Guayana Esequiba. The US State Department and the US Central Intelligence Agency (CIA), along with the British government, also played a strong role in influencing political control in Guyana during this time. The American government supported Forbes Burnham during the early years of independence because Cheddi Jagan was identified as a Marxist. They provided secret financial support and political campaign advice to Burnham's People's National Congress, to the detriment of the Jagan-led People's Progressive Party, which was mostly supported by Guyanese of East Indian background.