If built, the dam would dwarf the record-breaking Three Gorges Dam on the Yangtze River in central China -- with potentially serious impact for millions of people downstream in India and Bangladesh.

A report from China's official Xinhua news agency last month announced the project on the river -- known as Yarlung Tsangpo in Tibet and Brahmaputra in India -- linking it to Beijing's carbon neutrality targets and economic goals in the Tibet region.

China "has been urged to ensure that the interests of the downstream states of the Brahmaputra are not harmed by activities in upstream areas", India's foreign ministry spokesman Randhir Jaiswal said on Friday.

Jaiswal told reporters that New Delhi "will continue to monitor and take necessary measures to protect our interests".

India has established rights to river waters and "consistently expressed... our views and concerns... over mega projects on rivers in their (Chinese) territory," he added.

"These have been reiterated along with the need for transparency and consultations with the downstream countries following the latest report."

China's foreign ministry last month said Beijing "has always maintained a responsible attitude towards the development of cross-border rivers", and said the hydropower project "is aimed at speeding up the development of clean energy and addressing climate change".

"It won't have negative effects downstream", it said, adding that they "will also maintain communication with riparian countries".

Besides downstream concerns, in the past environmentalists have also warned about irreversible impact of such mega projects in the ecologically sensitive Tibetan plateau.

Both India and China, neighbours and rival Asian powers, share thousands of kilometres of disputed borders, where tens of thousands of soldiers are posted on either side.