NEW DELHI — India vowed Thursday to cut back on water flowing through its rivers to arid Pakistan, a threat it has made before but now seems more determined to carry out in the wake of a suicide bomb attack last week for which India has blamed Pakistan.

Nitin Gadkari, India’s transport minister, said in a Twitter message that “Our Govt. has decided to stop our share of water which used to flow to Pakistan. We will divert water from Eastern rivers and supply it to our people in Jammu and Kashmir and Punjab.”

Some analysts said this was the strongest threat India has made yet since the attack in which a suicide bomber killed more than 40 Indian troops in the disputed region of Kashmir.

A full-blown water war could be catastrophic to the hundreds of millions of people in India and Pakistan who depend on river water. But this latest threat was not accompanied by details on when or how India might act to divert more water from Pakistan downstream or how large, in reality, such diversions would be.