WASHINGTON — The Trump administration announced on Thursday that it would withdraw from Unesco, the United Nations cultural organization, after years of the United States distancing itself because of what it called the group’s “anti-Israel bias.”

The administration also cited mounting arrears at the organization as a reason for the decision.

“We were in arrears to the tune of $550 million or so, and so the question is, do we want to pay that money?” Heather Nauert, a spokeswoman for the State Department, said Thursday at a news briefing. She added, “With this anti-Israel bias that’s long documented on the part of Unesco, that needs to come to an end.”

While the United States withdrew from the group, the Trump administration said it wanted to continue providing American perspective and expertise to Unesco, but as a nonmember observer. The withdrawal goes into effect at the end of 2018, but that decision could be revisited, officials said.

If Unesco returns “to a place where they’re truly promoting culture and education on all of that, perhaps we could take another look at this,” Ms. Nauert said.