November 1945: Unesco founded by 37 countries in the immediate aftermath of World War Two, its purpose "to contribute to peace and security by promoting collaboration among nations through education, science and culture".
1974: Congress suspends US contribution after Unesco criticises Israel and recognises the Palestinian Liberation Organisation (PLO) - but later rejoins.
1984: Under President Ronald Reagan, US withdraws from Unesco, saying the agency is politically left-wing and financially irresponsible.
1985: UK withdraws, rejoining under change of government in 1997.
2003: US rejoins under George W Bush.
2011: US withdraws funding in protest at Palestinian membership of UN; arrears begin to accumulate.
2017: US announces it will withdraw entirely; Israel says it will follow suit.