The United States says it will back India's exemption from international rules on nuclear trade.

The global Nuclear Suppliers Group tightened rules on the exchange of sensitive nuclear technology last week, but outgoing U.S. Ambassador Timothy Roemer said Washington “strongly and vehemently” supports a waiver for India.

Roemer spoke at a ceremony in new Delhi Thursday marking his departure from the country.

The U.S. helped negotiate India's exemption from the old rules governing nuclear trade in 2008, allowing India to access nuclear technology and fuel even though it has not signed the Nuclear Non-Proliferation Treaty. As a result, India has not been required to open its nuclear facilities to international inspectors.

India is one of the world's fastest growing economies and the third-largest economy in Asia but has been continually plagued by electricity shortages.

New Delhi is relying on expanding its nuclear power program to meet the country's ever growing need for electricity.

The Reuters news agency says about 40 percent of Indians, or 500 million people, lack electricity.

During Thursday's ceremony, Roemer also praised the evolving ties between Washington and New Delhi.

He said the relationship had seen “significant success,” improving in a number of areas, including counterterrorism and humanitarian aid.