The US regularly took up with the Indian government the detention of Stan Swamy, who worked to "make the world a more just place", according to a State Department spokesperson.
"The US regularly raised Swamy's case with the Indian government as a part of our regular consultations on human rights and other bilateral issues," the spokesperson said on Tuesday.
Swamy, an 84-year-old Catholic Jesuit priest who had campaigned for Adivasi's rights, died on Monday while his bail application was pending with the Bombay High Court. He was detained by the National Investigation Agency (NIA) while probing allegations that he was linked to Maoists.
"We are saddened to learn of the death of Father Stan Swamy, a tireless advocate for the human rights of disadvantaged communities," the spokesperson said.
"Our condolences go out to Father Swamy's family and all those with whom he worked and mentored to make the world a more just place for us all."
The spokesperson did give details of when and at what levels the US had discussed Swamy's detention.
Swamy's detention by the NIA was mentioned in the State Department's 2020 International Freedom Report released in May.
It recalled that he was arrested "on sedition charges in connection with a violent demonstration that resulted in several deaths" and "his communication with others during detention was strictly regulated".
The Indian government has defended its treatment of Swamy and dismissed international criticism.
Earlier reacting to the UN High Commissioner for Human Rights Michele Bachelet's statement that she was "deeply saddened and disturbed" by his death, Indian External Affairs Ministry spokesperson Arindam Bagchi said he was held under "due process of law" and added: "Authorities in India act against violations of law and not against legitimate exercise of rights. All such actions are strictly in accordance with the law."
Indian Overseas Congress-US has said that Swamy's death was a "sad day for democracy".
The organisation's Vice President Geroge Abraham also called for the release of activist Sudha Bharadwaj and others on bail while awaiting charges.