Quoting senior Niger government officials, the newspaper said Herman Cohen, a former US assistant secretary of state for Africa called on Niger's president Mamadou Tandja, in the capital Niamey last week to relay the message from Washington.
One official told the Sunday Telegraph: "Let's say Mr Cohen put a friendly arm around the president ... but then squeezed his shoulder hard enough to convey the message, 'Let's hear no more about this affair from your government'. Basically he was telling Niger to shut up."
The Telegraph recalled that Hama Hamadou, Niger's prime minister, last week told it that the Niger government had never had discussions with Iraq about uranium, and called on British Prime Minister Tony Blair to produce the "evidence" he claims to have to confirm that Iraq sought uranium from Niger.
But US officials denied ever attempting to “gag” the Niger government.
"Basically he was telling Niger to shut up."
--Senior Niger official
The Niger official conceded that Washington’s warning was likely to be heeded.
"Mr Cohen did not spell it out but everybody in Niger knows what the consequences of upsetting America or Britain would be. We are the world's second-poorest country and we depend on international aid to survive."
On a visit to Washington last month, Blair maintained the accuracy of British intelligence on Iraq's alleged purchase of nuclear material from Niger, saying "we know for sure" that it bought 270 tons of the material from the African country in the 1980s.
Iraq's attempt to obtain nuclear material from Niger has become the focus of a political uproar in both the US and Britain after the Central Intelligence Agency publicly acknowledged the allegation should never have been in US President George W Bush's State of the Union address in January.
It was that link in particular, which was cited as one justification for the US-British invasion of Iraq.
Cohen's intervention in Niger suggested that Washington was keen to draw a line under the "uranium from Africa" affair, the Telegraph said, but added it had also learned that senior US soldiers were in Iraq last week to investigate movements of Niger's uranium.