The US has said “India remains a strategic partner”, treading cautiously in public after the department of justice announced in court that an Indian government official had directed a plot to assassinate an American citizen on US soil, but added that it had conveyed to New Delhi that it expected accountability.

Secretary of state Antony Blinken was asked on Thursday whether the US was “concerned that India is turning to tactics that violate international human rights law to silence its critics around the world”.

Blinken responded: “This is something we take very seriously. A number of us have raised this directly with the Indian government in past weeks. The government announced today that it was conducting an investigation, and that’s good and appropriate, and we look forward to seeing the results.”

India has not denied the allegation announced on Wednesday in Manhattan that an Indian government official had hired a narcotics trafficker and gunrunner to assassinate the US citizen, since identified as Khalistani separatist Gurpatwant Singh Pannun. The external affairs ministry has only said this is against government policy and that a probe has been instituted.

In two separate news conferences, the White House and the state department said they appreciated India’s decision to probe the case but were clear that they expected results and accountability.

At the White House briefing, National Security Council spokesperson John Kirby was asked how the alleged hit job would impact Indo-US relations, which are at a high point.

Kirby responded: “I will just say two things. India remains a strategic partner and we’re going to continue to work to improve and strengthen that strategic partnership with India.

“At the same time, we take this very seriously; these allegations and this investigation are taken very seriously. And, we are glad to see that the Indians are too by announcing their own efforts to investigate this. And, we have been clear that we want to see anybody that’s responsible for these alleged crimes to be held properly accountable.”

Kirby also made it a point to clarify that at the time Prime Minister Narendra Modi was hosted at the White House state dinner, the Biden administration was not aware of the assassination plot. “Remind you the state dinner happened before we knew about this,” he said.

President Joe Biden’s advisers say he emphasised during his meeting with Modi at the Group of 20 in India in September how seriously the US took the allegations, a senior US official who was not authorised to detail the conversation told The New York Times.

The justice department does not discuss ongoing investigations with White House officials, but criminal probes of foreign nationals that have foreign policy implications are flagged, according to current and former law-enforcement officials.

Then high-profile gatekeepers, including the national security adviser and the chief of staff, decide when and whether to brief the President.

In this case, the President’s advisers were briefed in late July, when it became clear that the case was not only a criminal investigation but involved the Indian government, according to a person familiar with the investigation.

By early August, Biden had dispatched top aides to New Delhi, officials said.

In October, Avril Haines, the director of national intelligence, travelled to India to lay out much of the material the government made public in Wednesday’s indictment, according to US officials.

A parade of US officials — including Haines, CIA director William Burns, Blinken and Biden himself — have confronted India in recent months with a message that Washington would not tolerate assassinations across North America, while asserting in public that relations between the two countries remain strong.

It has been a different approach than the one taken by Prime Minister Justin Trudeau of Canada. Relations between the two countries worsened after Trudeau accused the Indian government of involvement in the June 18 killing of Khalistani separatist Hardeep Singh Nijjar in a Vancouver suburb.

India rejected the allegation.

The Manhattan court documents, however, suggest a link between the plot to assassinate Pannun and the killing of Nijjar.

Additional reporting by the New York Times News Service