Pakistan is close to completing a second plutonium-producing reactor, is well into building a third and these could increase its ability to make atomic bombs, a US think-tank said on Thursday.
"The wider implication ... (is that) there is a real risk this will exacerbate an India-Pakistan nuclear arms race and increase tensions more broadly between the two," the Institute for Science and International Security said in a report.
The regional arch-rivals have fought three wars, are both outside the global Non-Proliferation Treaty (NPT) and have tested nuclear arms with Western technology imported ostensibly for peaceful atomic energy.
But a 45-nation nuclear export cartel approved a waiver to its rules this month allowing trade with India as part of a civilian nuclear cooperation pact it struck with the United States. The entire undertaking could erode the NPT, critics say.
ISIS, a well-connected Washington-based group, has been a prominent tracker of nuclear proliferation issues focusing on Iran, North Korea and Syria as well as Pakistan and India.
Emailed to Reuters, the ISIS report included commercial satellite images taken two weeks ago and in February and May showing construction of the second and third Khushab complexes.
Pakistan has an operating heavy-water reactor and heavy-water production plant already at Khushab.
A row of cooling towers indicated the second reactor was close to completion and could be ready to operate in a year's time, according to the 10-page report.
"Once completed, these reactors will increase several-fold Pakistan's ability to make weapons-grade plutonium (fuel)."
The report estimated the reactors would run on power of "about 100 megawatts or more", which could enable the two combined to yield plutonium for 8-10 atomic bombs a year.
"When finished, the second and third Khushab reactors will allow a significant increase in the quantity and quality of Pakistan's nuclear weapons."
The report said India could easily match Pakistan's moves given its own ability to churn out plutonium in heavy water reactors and a fast-breeder reactor under construction.
"Rather than witnessing a wasteful and dangerous surge in the production of fissile materials for weapons in South Asia, the United States should make a key priority convincing Pakistan to join negotiations on a universal, verified Fissile Material Cutoff Treaty," the report said.
U.N. negotiations on such a treaty, which would ban production of nuclear weapons fuel, have made no headway for years because of a lack of consensus among nuclear powers.
Pakistan built its first nuclear power station in 1972 with Canadian help. But Western countries, under pressure from Washington, later severed cooperation amid suspicion that Pakistan was covertly developing nuclear weapons.
Pakistan conducted five nuclear tests in 1998 in response to those of India, becoming a nuclear-armed state.