I would argue that they have, although it is somewhat indirect.

While nuclear weapons themselves would not have helped during the Indo-Chinese war of 1964, one effect was to massively increase Indian defence spending and for the first time Parliament debated the need for an atomic weapons programme. It is also worth remembering that nuclear weapons enable a variety of diplomatic options which otherwise wouldn't be available. Sisir Gupta (Sisir Gupta, “The Indian Dilemma”, in Alastair Buchan, ed., A World of Nuclear Powers? (Englewood Cliffs, N.J.: Prentice-Hall, 1966), pg 62) mentions that a non-nuclear India might be vulnerable to a kind of "nuclear blackmail" by China. Other Indian commentators have remarked that China was only taken seriously after it acquired a nuclear weapons capability, and imply that nuclear weaponisation is a precursor to being seen as a power. Menon (Rear Admiral Raja Menon, 2000, A Nuclear Strategy for India, New Delhi, Sage Publications India Pvt Ltd, pg 35) comments that in his hearing in 1994, Chinese delegates remarked that it was impossible for China to talk to India on any nuclear issues because India was not a nuclear power. Following the 1998 tests a security dialogue has been successfully established between the two countries, which Menon says offers an “…unpleasant corroboration of the value of power behind any diplomatic dialogue”.

In the case of Pakistan, the motive for nuclearisation seems to be the strategic relationship with India. While China may have accelerated India's drive to acquire nuclear weapons, Pakistan needed them in any case to attempt to redress the acute security dilemma it faced (especially after the results of the 1971 war with India). In this war Pakistan's main allies (the US and China) had not assisted it, meaning that Pakistan desperately needed some way of deterring Indian superiority in conventional arms.

So to summarise: China has played an indirect role in nuclearising India. However the Pakistani nuclear weapons programme would very likely have been conducted anyway.

who cares !... look where the higher densities of weapons are. That's where the problems are !... BY MENTALITY ! (them weapons did not get built by themselves !).

Now thermonuclear device is a need for India, If there is no need of power , why US is working for matter-antimatter devices? When we developed the weapon, our technology refines in every aspect of life.

It seems likely that India already has thermonuclear weapons. The Agni missile is reported as having a warhead with a yield of up to 250 kilotonnes, and while I believe that's achievable with a purely fission weapon it's far more likely this is a boosted-fission or thermonuclear warhead.

history has it that (large) H-bombs are of no military use - US and Russia have 0.4-0.5 Mt warheads.

That's loosely true, I suppose. Early H-bombs were large (some well over 5 Mt) to compensate for the inaccuracy of their delivery systems. But smaller nuclear weapons delivered more accurately are more "efficient", according to what I've read. Still, a nuclear attack doesn't have to be very big in order to ruin the lives of an awful lot of people.

Indian scientists , mostly high ranking administrative scientists without any knowledge of basic fusion reactions, coordinating Pokharan- II tests have cheated Indian people by fraudulently publicising the successful detonation of the fusion boosted thermonuclear device, tested at site -1 of Pokharan -II on May 11, !998. I have suggested the idea of a 'Jet spray volcano' to demonstrate unequivocally, whether the device was a fizzle or a complete dud. Jet spray volcano can be effected by drilling adeep bore from ground zero approaching the impacement center. My calculation suggests that the effort of BARC and DRDO scientists was for the assembly of big Megaton device not smaller than 1964 H-bomb tested by China.

Dear Chandra, when we test anything it does not mean completely failed or completely successful. Even a successful testing of any missile any country want full control and command on it. Therefore many test conducted. We got data even after failing a test. May be it will not very successful but in some respect it would be. India is a such a big country and everybody has a n number of idea even a high student. The same scenario with me also,when I am a high school student.When the age passes the number of ideas decreasing. Something is possible and something not with existing technologies whatever the thing present in India.

China was the first country in the region to built a nuclear weapon in 1960s. Due to the dispute between India and China on the Tibet, and the war between these two countries in the 1960s, India took the decision to built also a nuclear weapon. Taking into account the historical dispute between India and Pakistan since their independence from the UK, Pakistan also took the decision to build a nuclear weapon in order to reach a strategic balance between these two countries.

Based on the above we can said that China is responsible indirectly for the development of nuclear weapons in the subregion.

China did help Pakistan carry out some of its testing in the Lop Nor mountain range in Xinjiang if I am not wrong.

Dear Eram. Your are right, China assisted Pakistan in the development of their nuclear weapons programs in the past and is helping the country in the development of their nuclear power program for the generation of electricity.

so i guess it also answers the question posed, thanks Jorge