A top American official says a landmark nuclear deal between India and the US still faces difficulties but is hopeful it will eventually go through.
India must separate its civilian and military nuclear facilities
US Undersecretary of State Nicholas Burns made the remarks after two days of talks in the Indian capital, Delhi.
Under the deal India would gain access to US civilian nuclear technology.
Critics of the accord, which has to be ratified by the US Congress, fear it could harm non-proliferation efforts.
"The situation is unique, India's position is unique and there is complexity and difficulty to these talks which is inherent in the subject," Mr Burns told journalists in Delhi. The agreement hinges on India separating its military and civilian nuclear facilities and allowing international inspectors access to its civilian facilities.
Correspondents say that may not be very easy as some of the country's major research facilities are thought to straddle both fields.
Both countries also face domestic pressure.
Some US politicians and policymakers feel that making an exception in the case of India, which has not signed the Nuclear Non-Proliferation Treaty (NPT), would send a dangerous signal to non-proliferators, especially countries such as Iran.
On Friday, Mr Burns described Iran as a threat to global peace and said it had "overstepped the limits of international law in seeking to pursue its nuclear ambitions".
India wants to rid itself of US sanctions imposed in 1998
India, which voted against Iran at the IAEA last year, urged caution on both sides.
"It stands to reason that India which has with Iran a very longstanding... relationship, would not like see a situation of confrontation developing in a region that is very close to India," Foreign Secretary Shyam Saran said.
Indian and US officials have held several rounds of talks to resolve their differences especially ahead of the visit of US President George W Bush to India later this year.
Change in law
The agreement was signed last July during a visit by Indian Prime Minister Manmohan Singh to Washington.
Under the agreement, US companies will be allowed to build nuclear power plants in India, and also supply fuel for nuclear reactors.
The US imposed curbs on nuclear technology transfers to India in the wake of India's nuclear tests in 1998.
Delhi is keen on a deal on ways to share nuclear technology to help meet its growing energy needs.