The report, presented to General Hugh Shelton, chairman of the US joint chiefs of staff, recommended to encourage these countries to reform and become integrated into ``core'' US alliances, while maintaining the capability to respond to dangers and ``destabilising behaviour'' of these three nations.

Prepared by the influential National Defence University's Institute for National Strategic Studies, the report said, these countries are ``security strategy wild cards'' of US that could influence a ``best-case scenario'' in which other large powers are friends, sharing responsibilities, or they could shape a ``worst-case scenario'' encouraging instability, proliferation and challenge the US military supremacy.

The report said, ``In both cases, the US has and needs the ability to project power to protect its global interests.''

``In the best-case, its interests are secure and its ability to protect them is great, whereas in the worst-case, its interests are insecure and its ability to protect them is degraded,'' the report said.

The report has also cautioned the US to be on guard against these three powers as they could turn out to be either America's friends or challengers.

Of the three states that could cooperate or challenge, the report said, China is most likely to become a threat to the interests of US and its allies, whom it defines as ``core states.''

A large transition state (like these three nations) could ``turn away from the core, become hostile and strengthen its military forces. A large coalition could be constructed by the convergence of several hostile states.''

While the report recognises the potential security problems associated with Sino-Indian relations, it discounts the likelihood of Russia emerging as a major threat to the core of US alliances due to the latter's ``free-fall of industrial production, lack of domestic investment and the country's deteriorating human capital''.

In contrast, the study outlines concerns about Chinese nationalism, economic potential and some inherently conflicting interests with Washington that could pose a challenge US over the next 20 years.

It fears that a ``US-China showdown over Taiwan could materialise by 2018, and it is imperative that the United States have the offensive and defensive forces that could actually be used in such a crisis.''

The report recommends accurate weapons to destroy Chinese targets along with deployment of adequate defences ``to protect US forces.''