WASHINGTON-December is 'a very real deadline' for Iran to 'pursue its responsibilities' on the nuclear issue, White House spokesman Robert Gibbs warned on Tuesday. Reacting to Iranian President Mahmoud Ahmadinejad's rejection of a year-end deadline to accept a uranium-swap deal, Gibbs said while Ahmadinejad 'may not recognise the deadline that looms, but that is a very real deadline for the international community'. Ahmadinejad appeared on TV earlier in the day, dismissing the US backed deadline for Iran to accept a deal for swapping enriched uranium with nuclear fuel. '(You should) know that if we wanted to build bombs, we would have enough courage to announce that we were making bombs', Ahmadinejad said. The US and its Western allies have been accusing Iran of secretly developing nuclear weapons under the disguise of civilian nuclear power. Iran has denied the accusation and stressed its nuclear programme is only for peaceful purposes. Under a draft deal brokered by UN nuclear watchdog International Atomic Energy Agency (IAEA), most of Iran's existing low-grade enriched uranium would be shipped to Russia and France by the end of the year, where it would be processed into fuel rods with the purity of 20 per cent. The higher-level enriched uranium would be transported back to Iran to be used in the research reactor in Tehran for the manufacture of medical radioisotopes. Iran has rejected the deal, demanding a simultaneous exchange between low and higher level enriched uranium inside the country. The US has threatened another round of UN sanctions against Iran if it doesn't abide by the year-end deadline. 'We've begun to take steps, if Iran is unwilling to pursue its responsibilities', Gibbs warned. He said the international community 'have been waiting to see for months whether Iran will live up to its responsibilities'.