India summoned a senior US diplomat on Wednesday to explain reports that the US National Security Agency was authorised to spy on Prime Minister Narendra Modi's party before he took office, and to seek assurances this would not happen in future.
The US State Department said it would not comment "on every specific alleged intelligence activity," but a spokeswoman said she hoped that relations with the new Indian government, which Washington is keen to develop, would not be harmed.
According to a 2010 classified document leaked by former US security contractor Edward Snowden and published this week by the Washington Post, Modi's Bharatiya Janata Party (BJP) was among a handful of political organisations a US court allowed the intelligence agency to spy on.
The others included Lebanon's Hezbollah-allied group Amal, Egypt's Muslim Brotherhood, and the Pakistan Peoples Party, the leaked legal certification approved by US Foreign Intelligence Surveillance Court showed.
India's foreign ministry spokesman Syed Akbaruddin said that if the snooping reports were true, it would be "highly objectionable". The ministry said it summoned a senior US diplomat to seek assurances that any such surveillance would not occur in future.
"India has sought an explanation of the information contained in the press reports, and an assurance that such authorisations will not be acted upon by US government entities," it said in a statement.
State Department spokeswoman Jen Psaki declined to give details of what she called a "private" discussion.
"We have a deep and broad partnership with India," she told a regular news briefing. "We will discuss any concerns we need to discuss though private diplomatic channels."
Asked if the issue could have an impact on relations, she said: "We certainly hope not. We look forward to continuing discussions on a full range of bilateral and regional issues."
Psaki referred to an invitation by President Barack Obama for Modi to visit the United States and added: "We're looking forward to that, hopefully, in the fall."
Psaki also cited a Jan. 17 speech in which Obama said he was banning eavesdropping on the leaders of close friends and allies and had instructed US intelligence agencies "to work with foreign counterparts to deepen our coordination and cooperation in ways that rebuild trust."
The latest affair comes at a tricky time for Indo-US relations, which have been delicate for months following a major spat over the treatment of an Indian diplomat who was arrested in New York in December, an incident that was widely blamed for the resignation of the US ambassador to New Delhi.
The Obama administration has been seeking to revive ties since Modi's election in May, seeing India as a key strategic counter-balance in Asia to an increasingly assertive China. It is keen to ramp up bilateral trade and especially defence deals.
Modi was for years denied a visa for travel to the United States following religious riots in 2002 while he was a state chief minister. Even so, he has responded positively to the US advances and shown no resentment publicly.
Modi has not publicly commented on the spying allegation. BJP leaders offered cautious remarks that the government would take appropriate action. The foreign ministry had voiced concerns a year ago about allegations that US agencies spied on the Indian embassy in Washington, but critics say the issue has largely been brushed under the carpet.
The new row has overshadowed a visit to India by Republican US Senator John McCain, whose Arizona constituency is host to some of Boeing and Raytheon's most important defence businesses.
McCain, who told the Senate last week that Washington should seek to help India's economic and military development, cancelled a news conference due to be held outside India's foreign ministry after India summoned the US diplomat to explain the spying report.
US and Indian officials gave differing explanations for the cancellation, but said it was not linked to the row. McCain and India's Foreign Minister Sushma Swaraj discussed taking forward bilateral relations, the situation in Afghanistan and Iraq, foreign ministry spokesman Akbaruddin said. The United States does not currently have an ambassador in New Delhi and its most senior diplomat is the charge d'affaires.
According to Indian news reports, however, US Secretary of State John Kerry is expected to visit India at the end of this month, while Modi is expected to visit the United States in September.