U.S. Secretary of State Antony Blinken addressed the growing tension between Canada and India on Friday, saying the U.S. is “deeply concerned” about the allegations made by Prime Minister Justin Trudeau that India was involved in the murder of a Canadian citizen earlier this year.

Blinken, who spoke publicly at a news conference in New York City, is the highest-ranking U.S. official to discuss the matter, which has been escalating since Monday, when Trudeau accused the Indian government of being involved in the June 18 killing of Sikh activist and leader Hardeep Singh Nijjar.

Nijjar was gunned down in the parking lot of a gurdwara, a Sikh place of worship, in Surrey, a suburb of Vancouver in British Columbia. He was a vocal Sikh activist and proponent of the Khalistan movement, which aims to create an independent Sikh homeland in the Punjab state of India. The separatist movement began after the Indo-Pakistan partition of 1947, and is considered a controversial issue in India.