Pakistan's prime minister, Yousaf Raza Gilani, assured Barack Obama the country has an "appropriate safeguard" for its arsenal, understood to consist of 70-90 nuclear weapons.However, a report by Harvard University's Belfer Centre for Science and International Affairs, titled Securing the Bomb 2010, said Pakistan's stockpile "faces a greater threat from Islamic extremists seeking nuclear weapons than any other nuclear stockpile on earth".Experts said the danger was growing because of the arms race between Pakistan and India. The Institute for Science and International Security has reported that Pakistan's second nuclear reactor, built to produce plutonium for weapons, shows signs of starting operations, and a third is under construction.