BANGKOK — Rubber declined to the lowest level in six weeks as lower oil prices and a strengthening Japanese currency hurt demand for the commodity amid concern that the global economic recovery may falter. Thai supplies also gained.

The yen rose against the dollar after Federal Reserve Chairman Ben Bernanke said on Wednesday that the US economic outlook remains "unusually uncertain," boosting demand for Japan's currency as a refuge.

December-delivery rubber fell as much as 6.8 yen to 256.7 yen per kilogram ($2,968 a metric ton), the lowest level since June 9, before settling at 257.3 yen on the Tokyo Commodity Exchange. July-delivery rubber gained 1.5 percent to 357.2 yen, after rising 2.2 percent on Wednesday.