On issues from human rights to Ukraine, Indian Prime Minister Narendra Modi's record has raised alarm bells in Washington, but each time US officials decided the concerns should not derail the relationship.
Modi now faces his biggest risk yet after US prosecutors alleged that an Indian government official directed an assassination attempt on US soil -- but so far, President Joe Biden's administration is again hoping to keep tensions under wraps.
Two months after Canada alleged New Delhi's involvement in the killing of one of its citizens near Vancouver, the US Justice Department unveiled charges against an Indian man -- arrested in the Czech Republic on a US extradition request -- and alleged that an Indian official orchestrated the foiled plot.
In both cases, the targets were radical Sikh separatists promoting an independent state for their faith in the northern Indian state Punjab, where New Delhi crushed an insurgency three decades ago.
US presidents since the 1990s have sought a deeper partnership with India, saying the world's two largest democracies share common values.
But the new charges put India in the same league as Russia, Iran and Saudi Arabia which have faced US opprobrium for alleged transnational attacks.
"I think what we see is that the Modi government has become quite emboldened. This was such a brazen plot," said Lisa Curtis, a supporter of closer US-India ties who coordinated South Asia policy at the White House under former president Donald Trump.
"It sort of fits in line with other things that we've seen happening with the Modi government in terms of human rights, press freedoms and even its stance on Russia," said Curtis, now a senior fellow at the Center for a New American Security.
Journalists, activists and religious minorities have complained of harassment since the Hindu nationalist Modi took power in 2014, and India has rebuffed US calls to end its historic relationship with Russia over its invasion of Ukraine.
The United States sees India as like-minded on dealing with a rising China and has championed a greater role for New Delhi, including through the four-way "Quad" partnership with Australia and Japan.
Curtis said that Biden "appears to want to compartmentalize this issue from the broader strategic relationship."
Biden welcomed Modi with a gala state visit in June -- weeks after the Indian official made a first payment to the hitman, according to prosecutors -- and Secretary of State Antony Blinken and Defense Secretary Lloyd Austin visited New Delhi together in early November.
"As long as India takes the US concern seriously, and can somehow reassure Washington that something like this will never happen again in the future, then I think they can move forward," Curtis said.
- Quieter approach than Canada -
Aparna Pande of the Hudson Institute said that the pomp of Modi's visit and US enthusiasm for India's Group of 20 summit in September showed US priorities.
"For the US government, especially the Biden administration, a close partnership with India is critical to its grand strategy and national security goals," she said.
India responded furiously after Canadian Prime Minister Justin Trudeau went public with his own allegations, briefly curbing visas for Canadians and forcing Ottawa to withdraw diplomats.
Unlike Canada, where Sikh activists form an important political constituency, the United States chose a quiet approach which so far has been reciprocated.
Indian foreign ministry spokesman Arindam Bagchi said the US allegations were "a matter of concern" and "contrary to government policy."
Blinken, speaking to reporters Thursday in Tel Aviv, praised India's promise to investigate as "good and appropriate."
US officials said that Jake Sullivan, Biden's national security advisor, warned New Delhi against a new incident and that CIA Director Bill Burns visited India to raise US concerns directly.
- Indian fury -
Complicating US pressure tactics is Indian popular opinion, with Modi skilled in rallying nationalist fervor and commentators quick to accuse the West of hypocrisy, seeing as Washington has for years killed militants overseas -- although generally not in friendly countries.
Derek Grossman, a former US intelligence analyst now at the Rand Corporation, said the assassination allegations would only strengthen US critics, mostly on the left of Biden's Democratic party, who want more scrutiny of Modi and accuse him of turning India into an "illiberal democracy."
But Grossman expected the fallout to be "fairly minimal," noting that Biden already decided not to punish India over its purchases of Russian oil.
"The US is trying to integrate India into its Indo-Pacific strategy to counter China and the Biden administration at least hasn't shown any appetite to rock the boat on that," he said.