The UN conference on racism is expected to open in Geneva in April
The US is likely to boycott a UN racism conference, reports suggest, saying a text drawn up for the event criticises Israel and restricts freedom of speech.
An unnamed state department official said the draft document for April's forum in Geneva was "unsalvageable".
Canada and Israel have also said they plan to boycott the meeting.
In 2001, US and Israeli delegates walked out of a similar conference in Durban, South Africa, when a draft document likened Zionism to racism.
The 2001 draft expressed "deep concern" at the "increase of racist practices of Zionism and anti-Semitism".
It talked of the emergence of "movements based on racism and discriminatory ideas, in particular the Zionist movement, which is based on racial superiority".
A US delegation travelled to Geneva for negotiations earlier in February to try to agree the conference's final document.
"Unfortunately, the document being negotiated has gone from bad to worse," the unnamed state department official was quoted as saying by the Washington Post newspaper.
"The current text of the draft of the outcome document is, in the United States government's estimation, unsalvageable.
"As a result the United States will not participate in the forthcoming negotiations on this text, nor will we be able to participate in a conference that is based on this text," the official said.
Washington says the proposed text unfairly singles out Israel for criticism.
US officials say they are also concerned that some sections of the draft - which call for restrictions on the defamation of religions - could threaten free speech.