UNITED NATIONS - The Obama administration confirmed Wednesday in a letter to a US senator that it will boycott a world conference against racism being held at UN headquarters in September.

Joseph E. Macmanus, acting US assistant secretary of state for legislative affairs, wrote in the letter to Democratic Sen. Kirsten Gillibrand that the United States will not participate in the 10-year commemoration of the 2001 World Conference Against Racism because the Durban process "included ugly displays of intolerance and anti-Semitism."

Macmanus was responding to a letter the senator from New York had sent America's UN Ambassador Susan Rice asking her not to participate in the event.

"In December, we voted against the resolution establishing this event because the Durban process included ugly displays of intolerance and anti-Semitism, and we did not want to see that commemorated," Macmanus wrote.

He added that in 2009 the US withdrew from the planning of the conference because it reaffirmed the 2001 Durban Declaration, "which unfairly singled out Israel and included language inconsistent with US traditions of robust free speech."

"The United States delegation in New York has not been involved in the formal negotiations on the modalities resolution or the outcome document and has had a notetaker only in these proceedings," the letter added. "We share your concern about the Durban commemoration's timing and venue as just days earlier, we will have held solemn ten-year memorials for those murdered in the September 11 terrorist attacks."