The British newspaper said Britain's Foreign Office late last year ordered its diplomats in Kazakhstan, Uzbekistan and Brazil – all major uranium producers – to lobby their governments on the issue.
"Countries including Britain, the US, France and Germany have started intensive diplomatic efforts to dissuade major uranium producers from selling to Iran," the newspaper said.
The Western governments accuse Tehran of trying to acquire nuclear weapons under cover of a civilian nuclear energy program. Iran denies the accusation and says it only wants nuclear power in order to generate electricity.
The enriched uranium required for use in nuclear reactors or weapons is produced in centrifuges that spin uranium hexafluoride gas (UF6) at high speeds. The UF6 is derived in a chemical reaction from "yellow cake", a concentrate obtained from mined uranium ore.
The Times quoted sources as saying Iran had nearly exhausted its stock of yellow cake, of which it had acquired several thousand tonnes from South Africa in the mid-1970s.
A spokesperson for Britain's Foreign Office declined to confirm the Times report but said:
"It's essential to dissuade Iran from progressing towards the technology for a nuclear bomb. This risks sparking off a regional nuclear arms race. In a region which already faces huge security and other challenges, nuclear proliferation would be disastrous for stability."
The World Nuclear Association lists the top 10 uranium mining nations in 2007 as Canada, Australia, Kazakhstan, Russia, Niger, Namibia, Uzbekistan, the United States, Ukraine and China. Brazil was 13th.