Israel and Canada have already announced they will boycott the conference, which is known as Durban II.
According to Robert Wood, the US state department spokesman, the "document being negotiated has gone from bad to worse, and the current text of the draft outcome document is not salvageable.
"A conference based on this text would be a missed opportunity to speak clearly about the persistent problem of racism."
Wood said the US would not participate in the conference unless its final statement does not criticise any one country or conflict.
The US also did not want the document to take up the issue of reparations for slavery, which was another hot topic in the Durban 2001 conference.
Tzipi Livni, the foreign minister, welcomed the decision.
"Under the fig leaf of combating racism, this conference is blatantly anti-Semitic and anti-Israeli," Livni said in a statement on Saturday.
"The decision of the United States should be an example to other countries that share our values."
Pro-Israeli groups also hailed the US move.
"President [Barack] Obama's decision not to send US representation to the April event is the right thing to do and underscores America's unstinting commitment to combating intolerance and racism in all its forms and in all settings," the American Israel Public Affairs Committee said.
The Conference of Presidents, an umbrella group of more than 50 Jewish organisations, said: "It was clear from the preparatory meetings that this conference was again being hijacked by those who want to have a repetition of the first Durban conference, which focused almost singularly on Israel and was the occasion for vile and bigoted declarations and manifestations.
"It is our hope that the European countries will follow suit and announce that they will not participate."
US officials said they are pressing European nations to boycott the conference unless there are revisions to the final statement.
The Netherlands and France have already expressed concern about the contents.