India's Prime Minister Manmohan Singh has told the US Congress his country can be trusted with nuclear technology.
Mr Singh is being treated as an honoured guest in the US
US President George W Bush said on Tuesday he would push for Congress to lift sanctions on supplying civilian nuclear technology to Delhi.
Mr Singh told Congress that India and the US must draw on shared democratic values to boost trade and fight terror.
Correspondents say Mr Singh's US trip is set to cement a major alliance in the new diplomatic landscape.
The Indian leader on Tuesday became one of a small group of trusted allies invited to address both houses of the US Congress.
He told US lawmakers the "field of civil nuclear energy is a vital area for co-operation between our two countries".
India has obeyed all international laws aimed at checking the proliferation of nuclear technology, Mr Singh said, even though "we have witnessed unchecked nuclear proliferation in our own neighbourhood" - an apparent reference to neighbour Pakistan.
India and Pakistan conducted tit-for-tat nuclear tests in 1998, sparking sanctions and condemnation from the US.
President Bush's willingness to share nuclear technology with India marks an important shift in US foreign policy, correspondents say.
Mr Singh told Congress that India and the US had much in common: "You are the world's oldest democracy, we are its largest."
He said the "openness of our societies makes us more vulnerable" to terrorism.
He urged the US to invest in India's development, particularly in information technology.
"We are at a juncture in history where we can embark on a partnership that draws both on principle and pragmatism," Mr Singh said.
Congress also cheered as Mr Singh spoke of the need to reform the United Nations, arguing the case for India to be included on the Security Council - a proposal President Bush has opposed.
"The voice of the world's largest democracy cannot be unheard on the Security Council," he said.