The White House has begun to take steps to confront Iran's unwillingness to "pursue its responsibilities" on the nuclear issue, spokesman Robert Gibbs said on Tuesday.

"We've begun to take those steps, if Iran is unwilling to pursue its responsibilities," Gibbs said.

Iranian President Mahmoud Ahmadinejad on Tuesday dismissed a year-end deadline set by the Obama administration for Tehran to accept a United Nations-drafted deal to swap enriched uranium for nuclear fuel.

The deal aims to diminish Iran's stockpile of enriched uranium, easing the West's fears that the material could be used to produce a nuclear weapon. Iran, which denies it seeks to build a bomb, has balked at the deal's terms.

"The West can give Iran as many deadlines as they want, we don't care," Ahmadinejad told supporters in the southern Iranian city of Shiraz.

Lashing out at Washington, Ahmadinejad added: "If Iran wanted to make a bomb, we would be brave enough to tell you? Iran won't allow the U.S. to dominate the region."

Ahmadinejad told a U.S. news program on Monday that a reported confidential Iranian technical document describing Tehran's efforts to design an atomic bomb trigger was forged by Washington.

Ahmadinejad was asked by ABC News about a Times of London report last week on what it called a confidential Iranian technical document describing a four-year plan to test a neutron initiator, the part of a nuclear warhead that sets off an explosion.

"They are all fabricated bunch of papers continuously being forged and disseminated by the American government," he told the U.S. network in an interview in Copenhagen, Denmark, after he attended the United Nations conference on climate change.

Reports that Iran is working on a bomb trigger are "fundamentally not true," said Ahmadinejad.

The Times of London published on Dec. 14 what it said was the Farsi-language document, along with an English translation, entitled, "Outlook for Special Neutron-Related Activities Over the Next Four Years".

The document describes steps to develop and test parts for a neutron initiator, a device that floods the core of highly enriched uranium with subatomic particles to touch off the chain reaction of a nuclear explosion.

Last week Iranian Foreign Ministry spokesman Ramin Mehmanparast called the report "baseless ... not worthy of attention, intended to put political and psychological pressure on Iran."

Iran, the world's No. 5 crude oil exporter, says its uranium enrichment program is aimed at generating electricity so that it can export more gas and oil. The West believes Iran wants bombs from enrichment because of its record of nuclear secrecy.