The United States has charged a former Indian intelligence officer who allegedly directed a foiled plot to murder a Sikh separatist in New York City last year, with the FBI saying it would not tolerate retaliation against a U.S. resident.

An indictment of Vikash Yadav was ordered to be unsealed on Thursday. The U.S. Justice Department indictment mentioned Yadav as a former officer in India's Research and Analysis Wing spy service. It was filed in the U.S. District Court for the Southern District of New York.

Washington has alleged Indian agents were involved in an attempted assassination plot against Sikh separatist leader Gurpatwant Singh Pannun, a dual U.S.-Canadian citizen.

"The FBI will not tolerate acts of violence or other efforts to retaliate against those residing in the U.S. for exercising their constitutionally protected rights," FBI director Christopher Wray said in a statement.

An Indian government committee investigating Indian involvement in the foiled murder plot met with U.S. officials in Washington on Tuesday, a meeting that Washington described as productive.

The United States had been pushing India to look into the U.S. Justice Department's claim that an Indian intelligence official directed plans to assassinate Pannun.

The U.S. case is not the only instance of India's alleged targeting of Sikh separatists on foreign soil.

Canada on Monday expelled Indian diplomats, linking them to the 2023 murder of Sikh separatist leader Hardeep Singh Nijjar on Canadian soil. India also ordered the expulsion of Canadian diplomats and denies Canada's allegations.

The accusations have tested Washington and Ottawa's relations with India, often viewed by the West as a counterbalance to China.

India has labelled Sikh separatists as "terrorists" and threats to its security. Sikh separatists demand an independent homeland known as Khalistan to be carved out of India. An insurgency in India during the 1980s and 1990s killed tens of thousands.