Chairman of the US Joint Chiefs Martin Dempsey said Thursday that he did not want to be "complicit" if Israel chose to strike Iran's nuclear program, positing that a premature attack would dissolve the international pressure on the Islamic Republic, The Guardian reported.Speaking to journalists in London, Dempsey said an attack would "clearly delay but probably not destroy Iran's nuclear program," but added that the "international coalition" pressuring Iran "could be undone if it was attacked prematurely". "I don't want to be complicit if they [Israel] choose to do it," he added.Dempsey's comments come as the White House said that Iran had a limited window of time to stop its atomic work and diplomatic terms offered by the Western world will not remain open "indefinitely."A UN report released earlier in the day revealed that Iran doubled the number of uranium enrichment machines it has in an underground bunker, showing that Tehran continued to defy Western pressure to stop its atomic work and the threat of Israeli attack."We are closely studying the details of the report, but broadly speaking it is not surprising that Iran is continuing to violate its obligations," White House Press Secretary Jay Carney told reporters when asked about the UN International Atomic Energy Agency's (IAEA) quarterly report on Iran. "As the report illustrates, we are in a position to closely observe Iran's program," he said.