US thinktank raises concerns over Pak nuke threat to India - The Times of India NEW DELHI: Congressional Research Service ( CRS)), the US Congress's bipartisan thinktank for legal and political analysis, has warned in its latest report on Pakistan's nuclear programme that growing asymmetry in Indo-Pak conventional military capabilities could lead Islamabad to lower the threshold for using nuclear weapons. The report says the Pakistani government may consider fielding lower-yield nuclear weapons to increase the credibility of its nuclear deterrent vs. Indian conventional military operations. "In addition to making qualitative and quantitative improvements to its nuclear arsenal, Pakistan could increase the number of circumstances under which it would be willing to use its nuclear weapons," says the report titled, Pakistan's Nuclear Weapons: Proliferation and Security Issues. As it is, Pakistan's nuclear posture is deliberately unclear with ill-defined red lines. The intent is to keep India - and the world - guessing about under what circumstances the nuclear button will be pressed - the imminent collapse of the Pakistani state, a massive attack on its cities or even reverses near the border. The report says, Pakistan's nuclear arsenal consists of 90-110 warheads "although it could be larger" as against India's 60-100. While acknowledging that Pakistan has taken a series of steps to prevent proliferation of nuclear technologies and material, leading to improvement in nuclear security, it says instability in the country has raised a question mark over the "extent and durability" of these reforms expressing fear of proliferation by radical sympathizers in Pakistan's nuclear establishment. "While US and Pakistani officials continue to express confidence in controls over Pakistan's nuclear weapons, continued instability in the country could impact these safeguards," it says. The report goes on to say that Pakistan is not just producing more fissile material but also deploying additional delivery vehicles. "Pakistan continues to produce fissile material for weapons and appears to be augmenting its weapons production facilities, as well as deploying additional delivery vehicles - steps that will enable both quantitative and qualitative improvements in Islamabad's nuclear arsenal," it says. Only a few months ago, Pakistan had shocked the world as satellite images revealed that it was on the verge of completing work on the fourth reactor at Khushab, a plutonium-producing military facility. This has led to concerns in India that Pakistan is following the Chinese model of developing low-yield, tactical nuclear weapons which will provide it a "flexible" response in case of skirmishes at the border with India. While the report says Pakistan's nuclear warheads use an implosion design with a solid core of approximately 15-20 kg of highly enriched uranium, it adds that Pakistan is also actively producing plutonium for weapons. "It appears that Islamabad is constructing two additional heavy water reactors, which will expand considerably Pakistan's plutonium production capacity, at the same site (Khushab)," it says. Indian officials believe that the speed with which Pakistan has carried out work on the fourth reactor, a plutonium-producing facility, at Khushab could only have been made possible through a steady supply of uranium from China. There was no sign of this reactor in Khushab until 2009.