India has come a long way from being a "nuclear pariah" to a nuclear weapons state and it now needs to maintain a "credible nuclear deterrent" while avoiding accidental and inadvertent escalation, an expert has said.

Yogesh Joshi, a MacArthur Nuclear Security Post-Doctoral Fellow at the Center for International Security and Cooperation, Stanford University, and co-author of 'India in Nuclear Asia: Evolution of Regional Forces, Perceptions, and Policies', shared his views after the launch of the book at Teen Murti Bhawan in New Delhi.

"India has come a long way from being a nuclear pariah to a de facto nuclear weapons state. The need now is to see that India maintains a credible nuclear deterrent while avoiding dangers of accidental and inadvertent escalation," he said.

Joshi has authored the book with American scholar Frank O'Donnell. The books sheds light on the evolution of India's nuclear doctrine since 1999 and the challenges it faces.

India's first nuclear doctrine was declared in 1999 after the nuclear tests in 1998; it was revised in 2003.

"Twenty years after India became a nuclear weapons state, its nuclear capabilities have seen tremendous improvement. In the book, we have made two broad suggestions - New Delhi, Beijing and Islamabad should hold dialogues on nuclear issues, and a public defence review must be done by India," O'Donnell said.

A Stanton Junior Faculty Fellow at the Belfer Center for Science and International Affairs at Harvard University, O'Donnell said the work on the book began in 2013. The authors relied on public government statements for their research.

During a panel discussion after the launch, defence expert Arvind Gupta said: "India's nuclear doctrine is not for fighting a war, but meant to stop nuclear coercion and to make sure no one uses it against us."

He also referred to "credible minimum deterrence" mentioned in India's first nuclear doctrine in 1999.

According to the 1999 doctrine, "India's nuclear forces will be effective, enduring, diverse, flexible, and responsive to the requirements in accordance with the concept of credible minimum deterrence."

"While suggestions that India, Pakistan and China should have dialogue on nuclear issues sounds good theoretically but not very plausible practically. With China, nuclear is not the main issue... And jumping into a nuclear dialogue without proper security dialogue won't be very wise," Gupta said.

Providing an overview of India's nuclear forces as it stands in 2018, the book studies the implications that the nuclear postures of India's two main adversaries - Pakistan and China - have on its nuclear strategy.

The book explores India's relations with countries such as Iran, North Korea and Syria, and how these reveal India's global non-proliferation policy approaches.

It delves into key nuclear concepts such as 'no-first-use', 'credible minimum deterrence', 'full spectrum deterrence' and 'minimum deterrence' in the context of the emergence of the Arihant nuclear-armed submarine fleet and the Agni-V and prospective Agni-VI intercontinental-range missiles.