The government of Niger is being pressurised to sue the US for damages over allegations that Iraq tried to obtain uranium from the West African country.
President Tandja reiterated that Niger is innocent
The Chairman of the opposition Alliance for Democracy and Progress, Issoufou Bachar, says that Niger must seize the opportunity and file claims for "heavy damages".
"The US forged a letter on Niger's behalf ....this is a shame," local Tenere FM radio quoted Mr Bachar as saying.
US President George W Bush claimed in his State of the Union speech to Congress in January that Iraq had been seeking to acquire uranium from Niger for its nuclear programme.
But supposed documents backing up the claim were then shown to be crude forgeries, leading the White House to withdraw the charge.
President Mamadou Tandja of Niger on Sunday again rejected the claims, on the same day that Britain's Sunday Telegraph newspaper reported that the US was pressurising the West African country to keep quiet on the issue.
President Tandja also said that the International Atomic Energy Agency (IAEA), the UN's nuclear watchdog, had cleared his country of all suspicion.
"Even the IAEA cleared Niger of all suspicion before the United Nations Security Council," President Tandja said during an address to mark his country's 43rd anniversary of independence from France.
Niger is the world's third largest exporter of uranium after Canada and Australia, which between them account for about half the world's production.
In 1997, Uranium accounted for 70% of Niger's export revenues.