Washington: India could militarily intervene in Pakistan if Islamists gain control over nuclear weapons of its neighbour, either through a coup or a civil war, said a study by a US think tank.

"The nightmare scenario of the next few years is that American and allied military operations in South or South West Asia end up severely destabilising the Pakistani regime. Whether due to a coup by a more pro-radical Islamic faction within the military, or something close to outright civil war, the reliability of central control of the Pakistani nuclear arsenal will be diminished," said the study "Transforming America's Military", published by the National Defence University.

"In these circumstances, there would be the distinct prospect of Indian military intervention (with possible Israeli assistance), and the prospect of a major regional war in which the use of nuclear weapons could not be precluded," said the study written by Peter Wilson, a senior political specialist at RAND, and Richard D Sokolsky, a Distinguished Research Fellow in the Institute for National Strategic Studies at the National Defence University.

The study described India as "an important nuclear-armed ally of the US", and Pakistan "a very fragile ally".

India has become an "important nuclear-armed ally of the United States, providing diplomatic and material support for Operation Enduring Freedom. US rapprochement with India is consistent with the US low-profile, long-term containment or hedging strategy aimed at China," Wilson and Sokolsky said.

"Pakistan has become a vital but very fragile ally in the war against al-Qaida and the Taleban in Afghanistan," they noted.

PTI