Hoping to wean India from Iranian oil imports, Secretary of State Hillary Rodham Clinton is urging Indian leaders to explore alternative suppliers as she opens a three-day visit to the energy-starved South Asian nation that will also focus on regional security and easing trade restrictions. Clinton arrived in the eastern city of Calcutta on Sunday after visits to China and Bangladesh as officials traveling with her said the Iranian oil imports would top an agenda that includes India’s relations with nuclear rival Pakistan and the future of Afghanistan.