Allies have quit UNESCO after announcement in 2017, arguing it fosters anti-Israel bias.
The United States and Israel have officially quit the United Nations Educational, Scientific and Cultural Organization (UNESCO) at the stroke of midnight on New Year's Day, the culmination of a process triggered more than a year ago.
The withdrawal is mainly procedural yet serves a new blow to UNESCO, co-founded by the US after World War II to foster peace.
The withdrawals will not greatly affect UNESCO financially, since it has been dealing with a funding slash ever since 2011 when both Israel and the US stopped paying dues after Palestine was voted in as a member state.
Since then officials estimate that the US - which accounted for around 22 percent of the total budget - has accrued $600m in unpaid dues, which was one of the reasons for President Donald Trump's decision to withdraw. Israel owes an estimated $10m.
Officials say that many of the reasons the US cited for the withdrawal do not apply any more, noting that since then, all 12 texts on the Middle East passed at UNESCO have been consensual among Israel and Arab member states.
The State Department couldn't comment because of the US government shutdown.
Earlier, the department told UNESCO officials the US intends to stay engaged at UNESCO as a non-member "observer state" on "non-politicised" issues, including the protection of World Heritage sites, advocating for press freedom and promoting scientific collaboration and education.