It will be the largest global gathering on US soil in 65 years. President Barack Obama's two-day nuclear security summit, involving 47 countries, gets under way in Washington DC on Monday.<br /><br />On the sidelines of what is expected to be the biggest gathering of world leaders led by a US president since the signing of the UN charter in San Francisco in 1945,<br /><br />Obama will hold bilateral meetings with several leaders, including Manmohan Singh and Yousuf Raza Gilani, respectively the prime ministers of India and Pakistan.<br /><br />The US administration is trying to balance its policies in Afghanistan with the rising ambitions of the two neighbours.<br /><br />Robert Wirsing, an South Asia security analyst and professor of international politics at Georgetown University's Doha campus, explained the challenges facing the US to Al Jazeera's Imran Garda.
