NEW DELHI: India and the United States are close to signing a nuclear fuel reprocessing agreement, one of the last requirements to finalise last year's landmark civilian nuclear deal, an official said Sunday.

Indian National Security Adviser M.K. Narayanan told reporters "we have arrived at almost the very last stage" of negotiations.

Narayanan was speaking on board Prime Minister Manmohan Singh's plane as he returned from a Commonwealth summit in Trinidad and Tobago.

The establishment of nuclear reprocessing facilities under International Atomic Energy Agency (IAEA) safeguards is a critical component of the implementation of the Indo-US nuclear deal, sealed in 2008 with former US president George W. Bush.

The agreement allows India access to civilian nuclear energy despite its refusal to sign the Non-Proliferation Treaty.

Singh said on an official visit to Washington last week that he was confident US President Barack Obama would "operationalise the nuclear deal as early as possible."