MOSCOW (Reuters) - Russia edged closer on Thursday to an elusive 30-year gas supply deal with China that could be worth up to $1 trillion to help power Beijing's booming economy and allow Moscow to diversify its exports away from Europe.

An agreement on the gas project would be a big trophy for Chinese President Hu Jintao, who has courted Russia as a way of boosting energy security as robust economic growth increasingly forces China to look abroad for oil and gas.

For Russia, the deal offers state-controlled gas export monopoly Gazprom an alternative market, assuaging Prime Minister Vladimir Putin's concern of over-reliance on European customers.

While Hu has made securing energy for the world's second-biggest economy a diplomatic priority, relations with Russia, the world's largest energy producer, have not been smooth.