Leaders meet ahead of nuclear summit

US President, Barack Obama, has held a series of bilateral meetings with world leaders, in the run up to a nuclear summit in Washington. The summit, which begins Monday, aims to secure loose nuclear material around the world.

Obama, met with the Indian Prime Minister Monmohan Singh, South African President Jacob Zuma and President Nur-sultan Nazar-bayev of Kazakhstan. He is also expected to meet Pakistani Prime Minister Yusuf Raza Gilani. Obama said that efforts by terrorists groups, to acquire nuclear weapons, represented the biggest security threat.

U.S. President Barack Obama (R) meets with India's Prime Minister Manmohan Singh at Blair House in Washington D.C. April 11, 2010. Singh is in town for this week's nuclear security summit.REUTERS/Richard Clement