In a policy brief, the UN Conference on Trade and Development (UNCTAD) said market forces have caused "currency chaos" in the world and that international control of exchange rates would be better.
China, the world's biggest holder of foreign exchange reserves, renewed its commitment to the US Treasury market on Tuesday but said it would be wary of adding to its gold holdings.
China spreads out FX reserves risk - currency chief
Roubini cautious on yuan growth
China reaffirms to keep yuan basically stable