NEW DELHI — Indian Prime Minister Manmohan Singh's political future has come under a cloud over a controversial civil nuclear cooperation agreement with the United States that has helped isolate his party in Parliament.

At the root of the crisis is Singh's insistence that Parliament has no role in completing an international pact other than to be merely informed about it.

Singh's Congress Party holds only 26 percent of the seats in the ruling lower house of Parliament and runs a wobbly coalition government with the help of a number of smaller parties, including a leftist bloc that has now come out openly against the nuclear deal.