Washington has not sent Iran sufficient signals on whether the U.S. wants warmer relations and President Barack Obama''s support for Israel during its offensive in Gaza was "a major mistake," Iran''s president said in an interview broadcast Sunday.

Mahmoud Ahmadinejad''s comments highlight the mixed messages Iran has been sending to the Obama administration, which says it is reaching out to Iran to start a dialogue after decades of political deadlock.

Though Ahmadinejad has expressed a willingness for a new start with the U.S., the deeply polarizing figure also called Israel a racist country at a U.N. conference last week and blamed the U.S.-led invasion of Iraq on a Zionist conspiracy.

"We have welcomed such comments (from Obama). But an administration which, up until yesterday, was saying that I''m going to kill you, and today says that I''m not going to kill you, is that sufficient?" he told ABC''s "This Week" in a rare face-to-face interview with an American news network. The interview, which took place Wednesday in Tehran, was broadcast Sunday.

Ahmadinejad also questioned the Holocaust again, saying more study was needed to establish the historical facts.

"If this is a historically documented event, why do Western states show so much sensitivity toward a historical event? They do not want the lid to be taken off. I am asking them to permit studies," he said.