Western countries believe Iran has nearly exhausted its stocks of a raw material needed to make nuclear weapons and have started diplomacy to stop Tehran acquiring more, the Times reported Saturday.

Iran's supply of yellow cake uranium, which it acquired from South Africa in the 1970s, could run out within months, according to unnamed diplomatic sources quoted by the newspaper.

Diplomats from countries including Britain, the United States, France and Germany are lobbying governments in major uranium producing countries like Kazakhstan, Uzbekistan and Brazil not to sell Iran any more, the Times said.

While such efforts are unlikely to stop Iran from developing nuclear weapons, it could blunt its ambitions and help contain the threat, the paper reported.

Iran says its nuclear programme is for civilian purposes but many Western powers fear it wants to develop nuclear weapons and alter the balance of power in the Middle East.

Iranian envoy urges Obama to review Mideast policy
A special envoy of Iranian President Mahmoud Ahmadinejad urged US President Barack Obama on Saturday to fully review its Middle East diplomacy and respect Tehran's nuclear programme.

"If President Obama wants to realise a change, he should stop support for Israel and withdraw from Iraq," Samare Hashemi, on a visit to Japan, said in an interview with Japan's public broadcaster NHK.

He also said that relations between Iran and the United States would improve if Washington "respects rights" held by Iran, including its nuclear programme, according to NHK.

On Thursday, Hashemi handed Japanese Prime Minister Taro Aso a letter from Ahmadinejad saying that Iran wants to build closer ties with Tokyo for peace and stability in the Middle East, including Gaza.

Washington severed ties with Iran in 1980 in the wake of the Islamic revolution after Islamist students stormed the US embassy in Tehran and held 52 diplomats hostage for 444 days.

Obama's predecessor, George W. Bush, refused to engage in direct negotiations with Iran unless it first stopped enriching uranium, and spearheaded pressure for economic sanctions against the Islamic republic.