Delhi has asked the US to withdraw sanctions against two Indian scientists Washington says sold nuclear technology to Iran.
India is nuclear weapons-capable, as is its main rival, Pakistan
Indian foreign ministry spokesman, Navtej Sarna, said the scientists, C Surender and YSR Prasad, had made no such sale or transfer.
US State Department spokesman Richard Boucher made the allegations this week, although he did not name the Indians.
The men were barred from visiting the US or dealing with US-based companies.
The Indians were among 14 "entities", including seven from China and one each from Belarus, North Korea, Russia, Spain and Ukraine to face the sanctions.
Mr Boucher gave no details on whether the entities were individuals or firms.
Mr Sarna said India had conveyed to the US that it did not agree with its assessment on the Indians.
"No sale of materials, equipment and technologies was involved. No transfer of sensitive technology has taken place," said Mr Sarna.
He said that Mr Surender had never visited Iran.
"Dr Prasad initially visited Iran under a technical cooperation programme and thereafter he provided consultancy on safety related aspects connected with a nuclear power plant there which is under the International Atomic Energy Agency safeguards," Mr Sarna said.
"He has not visited Iran since mid-2003."
Mr Sarna said India's commitment to prevent proliferation was well known.