'Fundamentally not true'
In the ABC interview, carried out in Copenhagen, Denmark, after attending a UN climate change conference, Ahmadinejad said that the reports of the work were "fundamentally not true".
He said that the documents, which the Times said were in Farsi with an English translation, were "all fabricated bunch of papers continuously being forged and disseminated by the American government".
Ramin Mehmanparast, the Iranian foreign ministry spokesman, had already called the report "baseless" last week, adding that it was "not worthy of attention [and] intended to put political and psychological pressure on Iran".
Meanwhile, Iran's senior nuclear negotiator told Japanese officials on Tuesday that Tehran would never seek to develop a nuclear bomb.
Saeed Jalili told Yukio Hatoyama, Japan's prime minister, that weapons of mass destruction "are against Islamic teaching and that Iran would never develop such weapons," according to Hatoyama's office.
Hatoyama said that Japan was "concerned about the mistrust between Iran and the Western nations".
"He said Japan is prepared to play a role, if the both parties solve the mistrust and step toward peace," his office said.
Iran is under significant international pressure, particularly from the US, to end its nuclear programme.
Washington fears that the programme is intended to create nuclear weapons, but Tehran says that it is a peaceful attempt to develop nuclear energy for civilian use.
Meanwhile, the US has warned that the end of this month is "a very real deadline" for Iran to accept to a UN-brokered deal that would see it send its low-enriched fuel abroad.
Robert Gibbs, the White House spokesman, said on Tuesday that the US and its allies would "take steps" if Tehran did not accept the offer.
"We've begun to take those steps, if Iran is unwilling to pursue its responsibilities," he said.
Gibbs was responding to a speech by Ahmadinejad in which he appeared to dismiss the deadline.
"They say we have given Iran until the end of the Christian year. Who are they anyway? It is we who have given them an opportunity," Ahmadinejad said in the speech in the city of Shiraz.