India and the US began a crucial round of talks in New Delhi on Thursday on the nuclear issue, focusing on India's plan for separation of civilian and military facilities and the implementation of the July 18 landmark agreement between the two countries.

The Iranian nuclear issue, which threatens to snowball into a major issue, is also likely to figure at the two-day talks between Foreign Secretary Shyam Saran and US Under-Secretary of State for Political Affairs Nicholas Burns.

Burns arrived in New Delhi late on Wednesday night from Mumbai for the talks.

Saran visited the US in December and discussed the implementation of the deal.

The US insists on the separation of military and civilian facilities for Congress to give its final approval to the agreement.

The two jointly co-chair the Indo-US Joint Working Group that was formed to ensure the implementation of the July 18 agreement.

They have so far held three rounds of discussions.