TEHRAN/WASHINGTON (Reuters/AFP) - The US warned Iran on Tuesday that December is a very real deadline after Iranian President Mahmoud Ahmadinejad dismissed Wests ultimatum over its nuclear programme. Who are they to set us a deadline? Ahmadinejad said in a televised speech in the southern city of Shiraz. We set them a deadline that if they do not correct their attitude and behaviour and literature we will demand from them the Iranian nations historic rights, the President told the crowd, without elaborating. White House spokesman Robert Gibbs said the P5+1, which gathers UN Security Council veto-wielding permanent members Britain, China, France, Russia and the United States with Germany, were all on board on the deadline. Ahmadinejad may not recognise, for whatever reason, the deadline that looms, but that is a very real deadline for the international community, Gibbs said. Dismissing Western allegations about Irans nuclear ambitions, Ahmadinejad said: You should know that if we had any intention of building a bomb, we would have had enough guts and courage to announce that without any fear from you. Seeking to turn the tables on Irans old foes, he said the nuclear arsenals of the US and Israel should be dismantled. The Jewish state is assumed to have the Middle Easts only atomic weapons. They must know that the Iranian nation and all the worlds nations will continue resisting until the complete (nuclear) disarmament of America and all arrogant powers, he said. In an interview with ABC News broadcast on Monday, Ahmadinejad said a memo appearing to show Tehrans efforts to design an atomic bomb trigger was forged by the United States. Ahmadinejad was asked about a report in Londons Times newspaper last week on what it said was a confidential Iranian technical document describing a four-year plan to test a neutron initiator, the part of a warhead that sets off an explosion. They are all fabricated bunch of papers continuously being forged and disseminated by the American government, he said. On December 14, The Times published what it said was the Farsi-language document, with an English translation. The document described steps to develop and test parts for a neutron initiator, a device that floods the core of highly enriched uranium with subatomic particles to set off the chain reaction of a nuclear explosion.