There’s just one problem: To do that, India would have to violate a long-standing treaty that is the single most successful example of cooperation between the two nuclear-armed rivals.

The Indus Waters Treaty was signed in 1960 and governs six rivers that start in India but form a crucial lifeline for Pakistan. The agreement is a remnant of a different era, when relations between the two countries were not steeped in rancor. The treaty effectively gives use of three rivers to India and three to Pakistan.

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On Thursday, India’s water resources minister wrote on Twitter that the government had decided to choke off any flow to Pakistan from the three rivers India controls. But this was less an announcement than a reiteration of existing policy. India already uses about 94 percent of these waters and is moving ahead with projects to utilize what remains rather than let those waters flow to Pakistan.

Yet there is a clear desire in the government of Prime Minister Narendra Modi to do more. Three years ago, after a Pakistan-based group killed 19 Indian soldiers, Modi reportedly told government officials that “blood and water can’t flow together.”

On Friday, Nitin Gadkari, India’s water resources minister, said that there were calls for India to prevent even “a single drop of water” from going to Pakistan. But such decisions would have to be taken at “higher levels” of government.

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Talk of reducing water supply is a grave matter for any country, but especially one like Pakistan. Experts warn that Pakistan is on the brink of an era of water scarcity caused by a combination of factors — among them population growth, climate change and poor water management.

Conflicts between countries over water are expected to increase worldwide as the planet enters a period of perilous environmental change that includes persistent droughts and melting glaciers. But to use water as a form of warfare requires infrastructure — namely dams — that can take decades to build.

India’s rhetoric around water comes as its government is under intense public pressure to retaliate against Pakistan, and forms part of a pattern of “bombastic statements” over the past week, said Brahma Chellaney, a security expert and the author of two books on water and geopolitics.

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But Chellaney also believes that India should do more to use water as leverage with Pakistan. India could suspend its participation in the regular meetings of the commission that monitors the Indus Waters Treaty, he said, or stop the flow of data on water levels that India currently shares in real time with Pakistan.

“India can argue from a legal standpoint that Pakistan’s use of terrorism fundamentally changes the essential basis of the treaty,” Chellaney said. As the upstream country, India could also unilaterally decide to withdraw from the treaty, he said.

Such a move remains highly unlikely. Pakistan has warned that a move by India to exit the treaty would be perceived as “an act of war.” If India did decide to withdraw, its behavior would start to resemble that of another neighbor: China. China is notorious for refusing to enter into any water-sharing agreements like the Indus Waters Treaty with its neighbors and continues to build dams unilaterally on rivers that cross international borders.

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The fact that India has even floated the idea of breaching the treaty — an agreement that India and Pakistan have maintained for six decades — shows the depths of New Delhi’s frustration with Islamabad. But using water as a weapon is not as simple as it sounds.

Under the treaty, India has full use of the three eastern rivers in the system, while Pakistan gets the waters from the three much larger western rivers. India can also use the waters of the western rivers for certain purposes such as local irrigation and hydroelectric projects that do not restrict the flow of water.