Pakistan's nuclear arsenal is currently safe, but Washington has "concerns" over what could happen if the advancing Taliban topples the government, Secretary of State Hillary Clinton said in an interview with Fox News on Saturday. The security of Pakistan's nuclear arsenal is "an issue that we have very adamant assurances about from the Pakistani military and government. We've done a lot of work over the years evaluating that," Clinton told Fox News in an interview in Baghdad. "I think that the current thinking of our government is that it is safe," she said, according to a transcript of the interview. "But that's given the current configuration of power in Pakistan. "One of our concerns, which we've raised with the Pakistani government and military is that if the worst, the unthinkable were to happen, and this advancing Taliban encouraged and supported by Al-Qaeda and other extremists were to essentially topple the government for failure to beat them back -- then they would have the keys to the nuclear arsenal of Pakistan," Clinton said. "We can't even contemplate that. We cannot, you know, let this go on any further. Which is why we're pushing so hard for the Pakistanis to come together around a strategy to take their country back," Clinton told Fox. More than 1,800 people have been killed in a wave of Al-Qaeda and Taliban-linked extremist attacks across Pakistan since July 2007, when the military stormed the Islamist-occupied Red Mosque in Islamabad. The United States voiced concerns on Thursday over advances by the Taliban in Pakistan and said the issue was taking up a significant amount of President Barack Obama's time.