Pakistan, with a largely agriculture-based economy, fears that India may tamper with the 1960 Indus Water Treaty, brokered by the World Bank, following a rebel attack in India-administered Kashmir that killed more than 40 soldiers.
India says it is building dams to control water flowing into Pakistan-administered Kashmir.
The move comes as India seeks to punish its longtime rival for an attack on paramilitary soldiers by militants in India-administered Kashmir last week that left over 40 dead.
India's Water Resources Minister Nitin Gadkari said New Delhi would harness its share of unused water from three rivers to help Indian states.
Pakistan, a country of 200 million people with a largely agriculture-based economy, fears that India may tamper with the 1960 Indus Water Treaty, brokered by the World Bank, which calls for the unimpeded flow of three other rivers through India-administered Kashmir and farther into Pakistan proper.
The treaty has worked despite three wars between the two countries since 1947.
Under the leadership of Hon'ble PM Sri @narendramodi ji, 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.— Nitin Gadkari (@nitin_gadkari) February 21, 2019
Public pressure is mounting on the Indian government to consider revoking the water treaty if Pakistan does not accept its demand to stop what it says is Islamabad's role in training and arming insurgent groups fighting for Kashmir's independence or its merger with Pakistan.
Pakistan denies the charge and says it offers only moral and diplomatic support to insurgent groups and accuses India of human rights violations in India-administered Kashmir.
TRT World's Neha Poonia and Kamran Yousaf are following developments from New Delhi and Islamabad, respectively.
There was no immediate reaction from Islamabad to Gadkari's apparent threat to cut off water, but Pakistan's Foreign Minister Shah Mahmood Qureshi in a television interview earlier this week said that Indian leaders "have shown extreme irresponsible behavior by blaming Pakistan [for the Kashmir attack] without going into investigation about the incident."
He said that the Indian government had threatened to review the Indus Water Treaty.
On the issue of restricting or blocking the flow of water into Pakistan, Qureshi said, "This is an act of war and after seeing all these irresponsible statements of Indian leaders, I have written a letter to the secretary-general of the United Nations apprising him of Indian threats."
India withdrew most favoured nation trade status from Pakistan after last week's attack. India has vowed a "jaw-breaking response" to the suicide bombing, which was the worst attack on Indian forces since the start of the Kashmir insurgency in 1989.
Since independence from Britain in 1947, Pakistan and India – both nuclear-armed nations – have fought two of their three wars over Kashmir, which is divided between the two but claimed by each in its entirety.
India top court orders an end to assaults against Kashmiris
India's top court has ordered state authorities to stop threats, assaults and social boycotts of thousands of Kashmiri students, traders and professionals following the attack on paramilitary soldiers.
The Supreme Court acted on Friday on a petition filed by attorneys Colin Gansalves and Tariq Adeeb saying that Kashmiri students had to lock themselves up in several cities and towns to escape mob violence after the February 14 attack.
The attack in the Muslim-majority Kashmir Valley has raised tensions elsewhere in Hindu-majority India.
Most Kashmiris support rebel demands that their territory be united either under Pakistani rule or as an independent country, while also participating in civilian street protests against Indian control.