Rubber slumped by the most in eight months after US President Barack Obama imposed tariffs on tire imports from China, spurring concerns that demand in the world's largest consumer of the commodity may decline.

Futures in Tokyo fell as much as 7.8 percent, the biggest decline since Jan 13. The US imposed tariffs of 35 percent on $1.8 billion worth of tires from China, acting on a union complaint that imports were pushing US workers out of jobs.

"The news triggered sales of rubber futures," Kazuhiko Saito, chief analyst at Tokyo-based commodity broker Fujitomi Co, said. "The US action may not only weaken rubber consumption in China, but also have a negative influence on the global economy if retaliatory moves accelerate."