India's medal chances suffered a setback after a 1-3 defeat against Japan in the 12th Asian Men's Volleyball Championship being held in the north Chinese city of Tianjin.

India will now have to defeat the formidable Iran in order to remain in the medal hunt.

The Indian spikers, who had won all their three matches in the preliminary league, made their superior opponents fight for every point but committed some unforced errors to lose the second-round round-robin tie 22-25, 21-25, 25-23, 21-25 on Monday.

Meanwhile, defending champion South Korea swept away Group D winners Iran 3-0 on Monday, keeping the Indians hopes alive of making it to the semi-finals.

Iran has defeated Japan in their preliminary league match while India had got the better of Korea at the same stage.

"We lost the match against Japan due to some last-minute errors committed by our team," team manager B K Ojha said from Tianjin.

"If we can beat the powerful Iranian team we can still play for the 1-4 positions. But if we lose the match we would be fighting for the 5-8 positions," he said.

Earlier, China maintained their unbeaten run, thrashing Pakistan 3-0. The hosts, who have not dropped a set so far in the championship, crushed their opponents 25-16, 29-27, 25-17.

Fifteen teams are competing in the championship with the top two finishers qualifying for the World Cup to be held in Japan in November.