Washington: A US arms control expert has made the astonishing claim that India may have been the mysterious fourth customer of Pakistan's notorious nuclear scientist Abdul Qadeer Khan, dubbed father of Islamabad's nuclear bomb.

Journalist Joshua Pollack, a US policy wonk who has done work on nuclear proliferation, makes the assertion of all places in Playboy that Khan 'provided the shortcut to a nuclear weapon' to India besides Iran, Libya and North Korea.

The evidence he provides is pretty thin: 'Only three countries are known to operate centrifuge technology similar to Pakistan's. Two of them, Iran and North Korea, are already accounted for among Khan's customers'.

“The third and last country on the list: India, Pakistan's foe,' concludes Pollack, suggesting that it was 'an overlooked possibility, previously ignored because it seemed too absurd to consider, but it might be the most compelling answer to the fourth-customer mystery”.

Although India, which conducted its first nuclear test May 18, 1974, 'had beaten Pakistan to the bomb, they had done so through mastery of plutonium production - a different route to creating a nuclear weapon,' he said.

'India's ability to enrich uranium remained limited. New Delhi started a centrifuge programme in the 1970s, but the Indians weren't ready to break ground on their main enrichment facility until 1986.'

“By that point, Pakistan had been churning out weapons-grade uranium for at least three years,” Pollack claimed.

India's enrichment programme progressed slowly, but at some point before 1992 the Indians began experimenting with supercritical centrifuges, devices that can withstand very high rotational speeds, he said.

Documents the Indians gave potential suppliers for centrifuge parts 'provide strong clues about where New Delhi's supercritical centrifuge technology came from,' Pollack said.

“Despite some changes, the design is recognisable to the trained eye: It almost mirrors the G-2 centrifuge, a design that Khan stole from URENCO in the 1970s and later reproduced as Pakistan's P-2 centrifuge,” he said.

Centrifuge specs are not the only apparent link between India's enrichment programme and Khan's operation, Pollack claimed.

The cast of characters also overlaps, starting with Gerhard Wisser, a German living in South Africa, who also supplied India's centrifuge programme with specialised equipment, starting in the late 1980s, he said.