The membership in question was proposed by the President of the USA Barack Obama during his India visit in Nov 2010. Zamir Akram, Pakistan's ambassador to the UN, said that it could only increase tensions in the nuclear-armed South Asian region.
In a speech to the opening session of the UN sponsored Conference on Disarmament, he said, "These developments will amount to a paradigm shift in strategic terms," and added, "the message that such steps transmit is that the major powers can change the rules of the game if it is in their interest to do so."
The US has announced support for Indian membership of, the Nuclear Suppliers Group, the Missile Technology Control Regime, the Australian Group, which works to reduce the spread of chemical and biological warfare and the Wassenaar Arrangement, a joint effort by many nations to control the transfer of traditional arms and dual-use technology.
According to the UN nuclear watchdog, NSG rules, in order to import nuclear material all nations, with the exception of the five officially recognised atomic weapons states must place nuclear sites under safeguards of the International Atomic Energy Agency(IAEA).
But India's nuclear supply pact with the USA in 2008 ensured that it gets a waiver from the rules.