UPDATE 5-As Putin looks east, China and Russia sign $400 billion gas deal
* China-Russia gas contract signed during Putin visit
* 30-year deal took more than a decade to complete
* Political triumph for Putin, but terms vague
* China had upper hand in negotiations, experts said (Adds U.S. comment in paragraphs 13-15)
By Alexei Anishchuk
SHANGHAI, May 21 (Reuters) - China and Russia signed a $400 billion gas supply deal on Wednesday, securing the world's top energy user a major source of cleaner fuel and opening up a new market for Moscow as it risks losing European customers over the Ukraine crisis.
The long-awaited agreement is a political triumph for Russian President Vladimir Putin, who is courting partners in Asia as those in Europe and the United States seek to isolate him over Moscow's annexation of Ukraine's Crimea peninsula.
Commercially, much depends on the price and other terms of the contract, which has been more than a decade in the making.
China had the upper hand as talks entered the home stretch, aware of Putin's face-off with the West. Continued...