The farm produce prices are expected to drop as more vegetable dealers get to know the preferential policy and transport their goods to Beijing, he said.

The major supermarkets in Beijing also have ample supplies.

"Our company increased purchases before the truck ban and the price is stable in all our stores," said Huangli, a Wal-Mart public relation manager.

Beijing Municipal Development and Reform Commission, the city's planning body, has recently promised not to increase prices of any products during the Olympics to ensure a stable market.