Any such deal would violate United Nations sanctions imposed on Iran in 2006 over its nuclear programme. Uranium ore, also known as "yellow cake", can be enriched to use for fuel either for reactors or nuclear weapons.
An intelligence report by an unnamed member nation of the United Nations' International Atomic Energy Agency said Iran was willing to pay $450 million for the uranium and that the clandestine deal, to be sealed with Kazakh state employees acting without the approval of the Kazakh government, could be completed within weeks.
"Such fabrications of news are part of the psychological warfare (against Iran) to serve the political interests of the hegemonic powers," Iran's representative at the United Nations said, Reuters reports.
News agencies also report, Iran and Kazakhstan have both refuted reports of a secret deal by which Iran would procure uranium, Israel Radio reported Wednesday afternoon.
According to a separate report by Army Radio, Iran claimed that the accusations against it were part of a psychological war, Jerusalem Post reports.
Purified ore, or uranium oxide, known as yellowcake, is processed into a uranium gas, which is then spun and respun to varying degrees of enrichment.
Low enriched uranium is used for nuclear fuel, and upper-end high enriched uranium for nuclear weapons.
Commenting on the leaked intelligence report, Ian Kelly, the US state department spokesman, said "the transfer of any uranium yellowcake ... to Iran would constitute a clear violation of UNSC sanctions".
"We have been engaged with many of our international nonproliferation partners on Iran's illicit efforts to acquire new supplies of uranium over the past several years," he said.
Kazakhstan is among the world's three top producers of uranium, accounting for more than 8,500 tons last year, Aljazeera.net reports.
British Foreign Secretary David Cameron said that Russian President Vladimir Putin should be outvoiced about the crisis in Ukraine. In order to do this, the West needs to provide even greater support for Kyiv