There is nothing.. the US or IN can do about Gwadar....
1) IF Pakistan approve PLAN in thier water....... there is nothing.. the US, IN or even UN secuity counil (which China is one of the 5 nation with veto power) can do.... meaning "sanction" or Military action. becos it's there right to do so and it doesn't break any internation laws.
2) There maybe alot of military tension in the area if there is a PLAN present, but it unlikely going to turn in to a war. As long as the PLAN keep there ship and plane.. within Paskistan and internation airspace/Water, any action taken by the US or IN will be know as unjustified hostile and in turn US or IN may face internation pressure, mayber even the UN secuity counil. What are they going to said, they attack cos they dun like them being there.
3)Any Saction or military action against Pakistan is highly unlikey for a long time, cos US depend.. on Pakistan side with it war on terror, and Afghanistan's. If the Pakistans decide to let there border with Afganistan uncheck, they may jeopardize it large aid package from America or face some kind of saction, but they still have China to help them, but Afghanistan might be crippled and the US going have a hell of a time in there. Then most likely the terrorist will do most the physical dmg. It be come a loss-loss situation, the only one who maybe get something out of it is the terrorist.
4)Military action against China is out of the question.
Saction highly unlikely, cos guess which economies going be hurt the most.
It becomoe another loss-loss situation
Here is the FACT.
The america's net national saving rate fell into negative territory in later 2005, at minus 1.2 percent of the national income. This means the US doesn;t save enough even to cover the replacement of worn-out plants and equipment. The frist for any hegemonic power over a much longer span if world history. Faced with a shortfall of domestic saving, countries can curtail economic growth or blorrow from the rest of the world. The frist option just doesn;t cut in the land of abundance. That leave the second option: borrowing. So America must run a massice current-account deficit to attract the foreign capital it needs to fund economic growth and now closing in on $800B per or about $3B er business day, up for $2B 2 years ago. That where China fit into America equation, thank to China, the US got a rather extraordinary deal for its trade-deficit dollar in 2005, a net balance of some $200B in low-cost, high-quality Chinese made goods that enlarged the purchasing power of American consumers. Therefore if any saction, high tariffs or a major Chinese currency revaluation who greatly impact the US economics as a whole. The absent of China's supply line the trade deficit wouldn't shrink, but instead who merely gravitate toward other foerign producters, which most likily dun enjoy China's low-cost and pricing advantages, therefore increasing US foregin debt.
Yeah another point, What would happen if china dump all it US foregin currency and buy EU. But i know this is impossible.
US also need China help with IRAN and most importantly N.Korea.
5) For your infomation the IN isn't dat great, it a powerful navy in Asia. But it pretty much still a coastal defence fleet. It may have a carrier, but it still doesn't have the power to fully protect the carrier and protect the rest of it coast at the same time if the carrier move outside it national water.