CHICAGO (AFP) - Irans nuclear ambitions are the greatest current threat to global security, US Defence Secretary Robert Gates said Thursday. Iran is the one that concerns me the most because there dont seem to be good options (or a scenario) where one can have any optimism that good options will be found, Gates told the Economic Club of Chicago. The threat rests not only in Irans apparent determination to seek a nuclear weapon, but in the inability of the international community to affect their determination to do that, Gates said. All of the outcomes are negative, he said. If they achieve one, the possibility of a nuclear arms race in the Mideast is very, very real. If something is done to prevent them from getting one, the consequences of that are completely unpredictable and frankly, very bad. The US Defence Secretary said he would fight lawmakers to ensure cuts to the F-22 fighter programme, saying it was a test of efforts to reform entrenched military spending. It is time to draw the line on doing defence business as usual, Gates said in the speech, adding that President Barack Obama would make good on a threat to veto any defence budget that includes money for new F-22 Raptors. The president has drawn that line. And that red line with regard to a veto is real. Gates portrayed the issue as a crucial test of whether military spending could be reformed and the defence establishment weaned away from habits formed during the Cold War. If we cant get this right, what on earth can we get right? Gates acknowledged that previous administrations have struggled to rein in Pentagon spending and encountered stiff opposition from lawmakers and their sponsors in the defence industry. But he said the stakes today are very high with the country at war in an increasingly volatile world. The defence secretary, a Republican holdover from the Bush administration, said he had always been known as a hawk on national security during his long career at the Central Intelligence Agency. Gates blasted what he called requirements creep in defence spending, where weapons programmes were overloaded with unnecessary features to the point of absurdity.