U.S. officials roundly condemned Iranian President Mahmoud Ahmadinejad Monday for using an anti-racism conference in Geneva as a platform for lambasting Israel. 

White House Press Secretary Robert Gibbs called the tirade "hateful rhetoric" and cited Ahmadinejad's behavior as one of the reasons the U.S. boycotted the United Nations conference. 

"The president disagrees vehemently with what was said, as from some of the video I saw, so did many others," Gibbs said. 

He was referring to the dozens of representatives, mainly from Europe, who walked out of the U.N. conference in protest of Ahmadinejad's address. Several other countries, including the United States, boycotted the conference before it began, largely because they expected it to be used as a venue for anti-Israel rhetoric. 

Ahmadinejad on Monday called Israel the "most cruel and racist regime" and blamed Western countries for the financial crisis. He also called the Holocaust a "pretext" for aggression, on the eve of Holocaust Remembrance Day. 

"I think the president and the administration, obviously, made the right decision in not going forward with attendance at this conference, despite, obviously, a president that believes greatly that racism and intolerance must be and should be addressed," Gibbs said. 

State Department spokesman Robert Wood told reporters that Ahmadinejad's remarks "frankly, were unacceptable and, frankly, feed racial hatred." 

"Iran needs to end this type of inflammatory rhetoric. It's not helpful," Wood said. "This is not rhetoric that should be used in the 21st century." 

President Obama has made several overtures to the Muslim world, including Iran, prompting Ahmadinejad to say his country "welcomes a hand extended to it" earlier this month. 

Despite Monday's anti-Israel rhetoric, Wood said the Obama administration still wants to engage Iran diplomatically. 

"In the end, it's going to be up to Iran, but this administration has said it's willing to engage in direct diplomacy," Wood said. 

FOX News' Nina Donaghy contributed to this report.