MOSCOW, June 17 (Reuters) - The presidents of Russia and China on Wednesday agreed to boost the use of their national currencies, the rouble and yuan, in bilateral trade.

"It is essential...to move forward the work on the creation of favourable conditions for widening the sphere of settlement in roubles and yuan," Russian President Dmitry Medvedev and Chinese President Hu Jintao said in a joint statement.

Russia, the holder of the world's third largest reserves after China and Japan, has repeatedly called for less global reliance on the U.S. dollar -- in which the bulk of the world's reserves are held and most global trade deals are made.

Moscow has said the rouble and the yuan could become global reserve units in the future, and also suggested the creating of a supranational reserve currency, possibly based on the International Monetary Fund's Special Drawing Rights.

China, which holds nearly $2 trillion in foreign currency reserves and does not want to see the value of its dollar assets go up in smoke, has not joined in the dollar criticism.

But with trade between Russian and China worth $10.7 billion dollars in the first four months of this year alone, greater use of national currencies could have an impact on the greenback.