Dec. 20, 2009— -- Iran's president is dismissing a newly revealed secret document that purportedly shows Iran has been trying to develop a crucial component of a nuclear bomb, calling it a fabrication concocted by the U.S. government.
In an exclusive interview with ABC News' Diane Sawyer, President Mahmoud Ahmadinejad refused to look at a copy of the document, waving it away.
"No, I don't want to see this kind of document. These are some fabricated papers issued by the American government," he said.
Watch Diane Sawyer's interview with Iranian President Mahmoud Ahmadinejad Monday night on "ABC World News with Diane Sawyer."
It was the first public comment by the Iranian leader on the two-page document since its existence was revealed by The Times of London last week.
According to the newspaper, the document shows Iran has been secretly working on testing a neutron initiator -- the part of a nuclear bomb that triggers an explosion. The technology has no use aside from detonating a nuclear weapon.
Critics of the Iranian regime have seized on the revelation as a smoking gun -- one of the strongest indicators yet of a continuing nuclear weapons program in Iran.
But when asked point-blank whether Iran had been testing a neutron initiator, the Iranian president was dismissive.
"I think that some of the claims about our nuclear issue have turned into a repetitive and tasteless joke," Ahmadinejad said in the interview.
Asked about Ahmadinejad's allegation that the U.S. government fabricated documents, White House Senior Adviser David Axelrod said: "Of course that's nonsense."
"Listen, nobody has any illusions about what the intent of the Iranian government is -- and we've given them an opportunity to prove otherwise by allowing them to ship their nuclear material out [of Iran] to be reprocessed for peaceful use," Axelrod told George Stephanopoulos on ABC News' "This Week." "And they have passed on that deal so far. And the international community is going to have to deal with that if they don't change their minds."
Sawyer interviewed Ahmadinejad in Copenhagen, Denmark, after he attended the United Nations conference on climate change. The interview will be broadcast Monday night on "ABC World News with Diane Sawyer."
The Times of London caused an international stir last week with its claims about the two-page Iranian document.
The newspaper reported that the document describes a four-year plan to develop the neutron initiator, and that it apparently was written in early 2007, which would mean that the arms work could be near its conclusion.
Iran and the West are increasingly at odds over the Islamic republic's nuclear program. Iran insists its nuclear activities are peaceful and are only meant to generate electricity for civilian use.
But the United States and its European allies fear this "civilian" program is a cover to mask the development of nuclear bombs.
President Obama has set a year-end deadline for Iran to comply with agreements to ship its weapons-grade uranium out of the country, or face the threat of new international sanctions.
Axelrod said the threat of sanctions was real.
"When we came to office, Iran was united and the world was divided in an approach to deal with Iran," Axelrod said. "Today, Iran is bitterly divided, and the world community has come together, and the president has been a big force in bringing them together.
"Plainly, there are going to be consequences if they [the Iranians] don't turn around," he added.
Although Iran has shown little willingness to comply with the demand to ship uranium abroad, Ahmadinejad insisted in his interview with ABC News that he has not ruled out new talks on nuclear issues.
"We have not closed the dialogue window," he said. "If they are ready we are also ready to continue the dialogue and discussion."