Six months after Indian PM Modi addressed the US Congress, Joe Biden has turned down an invitation for India’s Republic Day parade after the US alleged an Indian link to a planned assassination on its soil.

Indian Prime Minister Narendra Modi is not known to give interviews to the media.

In late December he made an exception and spoke to the London-based Financial Times, which had first reported on how the United States government had thwarted an alleged plot hatched by an Indian agent to kill a Sikh separatist on American soil. New York-based Gurpatwant Singh Pannun, a US-Canada dual citizen, has been branded a “terrorist” by India for issuing threats of violence against New Delhi and for his call for a separate Sikh homeland carved out of India, called Khalistan.

In the interview, Modi made light of suggestions that the US allegations of Indian involvement in an attempted extraterritorial and extrajudicial killing had hurt bilateral ties between the world’s two largest democracies. “I don’t think it is appropriate to link a few incidents with diplomatic relations between the two countries,” he said while committing — as his country’s Ministry of Foreign Affairs had done earlier as well — to an internal Indian investigation into the allegations.

Yet a series of visits — and one key decision to avoid a visit — point to a strain in ties at a time when both nations are headed towards elections, shrinking the political space available to their leaders to make moves that could attract domestic criticism.

On December 11, FBI chief Christopher Wray visited New Delhi for talks that are believed to have included a conversation on the Pannun case — it was the first visit by an FBI director to India in 12 years. The US Congress-appointed watchdog on religious freedom also released its annual report early, demanding that the Biden administration declare India a “country of particular concern”. The US Commission on International Religious Freedom linked the allegations of a hit ordered against Pannun to the broader concerns about attacks on religious minorities in India. It said it was “alarmed” by India’s increased transnational “targeting of religious minorities and those advocating on their behalf”.

Then, US President Joe Biden turned down Modi’s invitation to attend India’s January 26 Republic Day celebrations as chief guest. No formal reason has been made public, but Biden’s refusal to come to New Delhi has also forced India to postpone a meeting of the Quad grouping — which also includes Australia and Japan — it was hoping to hold during the US leader’s visit.

These are among a series of “signs” of the tensions in ties, said Sushant Singh, a senior fellow at the New Delhi-based Centre for Policy Research.

“June was the high peak of India-US ties and they have cooled down since,” he told Al Jazeera, referring to Modi’s visit that month to Washington, during which he became a rare leader to address the US Congress for a second time. “The Pannun murder plot has had a definite role to play in this.”

hat doesn’t mean that India-US relations are in any serious trouble, said Christopher Clary, an assistant professor of political science at the University of Albany and a non-resident fellow at the Washington-based Stimson enter. Besides the Pannun episode, he told Al Jazeera, relations between the two countries were fine.

“This is like a commercial airliner that encounters turbulence,” he said. “It can be unpleasant for those aboard but does not endanger the aircraft. We will keep flying even if we encounter bumpy air sometimes.”

Clary said that “shared US and Indian concerns about a rising China can paper over many potential US-India differences.”

Still, in India, a refrain — from influential voices in the strategic community to people on the street — has gained ground that New Delhi did no wrong if it indeed tried to assassinate Pannun. “If the US can kill Osama bin Laden on foreign soil, then what stops us,” asked an analyst who requested anonymity because of concerns that his candid comments might affect his ability to work on bilateral relations. “Why different yardsticks?

Yet India too has deployed different responses to the US allegations, and similarly dramatic assertions by Canada that New Delhi might have been behind the assassination of another Sikh separatist, Hardeep Singh Nijjar, in the town of Surrey near Vancouver.