WASHINGTON - The U.S. is satisfied so far with India's moves to ensure accountability in alleged assassination plots against Sikh activists, but many steps are still needed, the U.S. ambassador to India said on Thursday, calling it a "red line for America" for which there must be consequences.

Eric Garcetti was asked at a U.S. think tank event what effect the recent discovery of assassination plots against Sikh nationalists in Canada and the United States could have on Washington's relations with New Delhi.

"When I was referring to a relationship that might have bumps along the road, this would be potentially the first big fight in a relationship," he told the Council on Foreign Relations.

"So far, knock on wood, I would say the administration is satisfied with the accountability that we've demanded on this, because this is a red line for America, for our citizens, and a core part of what we need to do," he added.

Garcetti said a criminal case and indictment had been brought "and if there is any connection to state actors in that, there has to be accountability."

"We expect that not only from our side, but we expect India to have that accountability."

Garcetti noted that India had set up a commission of inquiry "and ... we expect while we do the criminal case that is about American justice, that there need to be consequences and shared information.

"And so far ... I have been satisfied with what they have done. I think the administration is, but we have many steps still to go."

In November, U.S. authorities said an Indian government official had directed the plot in the attempted murder of Gurpatwant Singh Pannun, a Sikh separatist and dual citizen of the United States and Canada.

The White House said last month it viewed the reported role of the Indian intelligence service in the assassination plots as a very serious matter.

It made the comment after the Washington Post reported that an officer in India's intelligence service was directly involved in the foiled plan in the U.S. and also involved in the separate shooting death of a Sikh activist last June in Canada.

Canadian police on Friday arrested and charged three Indian men with the murder of Sikh separatist leader Hardeep Singh Nijjar last year and said they were probing whether the men had ties to the Indian government.

India has expressed concern about the linkage to officials and dissociated itself from the plot, saying it would formally investigate the U.S. concerns, and take necessary follow-up action on the findings of a panel set up on Nov. 18.

The issue is a highly delicate one for both India and the U.S administration as they try to build closer ties in the face of shared concerns about China's growing power. REUTERS