The tweet, published at 9:14 p.m. ET on Thursday, urged American expats to share a voter registration tool on the website of the activist organization Avaaz that states, "U.S. Citizens abroad could defeat Trump ... if they voted."

The Web page, titled "The October surprise that will end Trump," allows users to sign up for help registering to vote in the Nov. 8 presidential election and encourages them enlist their friends as well.

"At a time when Trump is trying to divide us, we could help defeat him if we all share this page with EVERYONE. Let's reach every US voter abroad," it reads.

The tweet was deleted within 20 minutes, without explanation.

Ari Gaitanis, chief of the U.N. News Services Section, which oversees the twitter account, said it was a mistake.

"That tweet did not originate from the UN News Centre and this was the reason for it being taken down," he told POLITICO.