Hoping to wean India from Iranian oil imports, U.S. 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 giant that will also focus on regional security and easing trade restrictions.

Clinton arrived in the eastern city of Kolkata — the first secretary of state to visit the former colonial capital of 14 million — 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.

India has huge energy needs to fuel its rapid growth and has made some progress in easing its dependence on Iranian oil. But a senior U.S. official said the United States wants to see more.

The official, who spoke on condition of anonymity to preview Clinton's private discussions in Kolkata and New Delhi, said the "trend lines are good" but "we really need to receive assurances that they are going to continue to make good progress."