PANAMA CITY--Japan has overtaken China to become the second-biggest user of the Panama Canal amid an escalating trade war between Beijing and Washington, canal authorities said Thursday.

China's slip to third is due to decreased shipments of natural and liquid petroleum gas as the Asian giant is buying less of them from the United States, administrator Jorge Quijano told reporters, adding that at least 2 million tons of gas are not being moved through the canal as a result.

Quijano said there is also a decrease in container traffic between China and the U.S.: Cargo ships "are not contributing as much as before because they come with lots of empty space," he said.

Quijano said it would be premature to speculate whether the drop in shipping between China and the United States would affect canal earnings forecast for the current fiscal year through the end of September.

"We had a very good May, we can't complain," Quijano said. "Hopefully that is repeated in June and we may be able to be above what has been budgeted.

The United States remains the biggest user of the canal. During the last fiscal year, 174.9 million tons of cargo were shipped to and from the country through the waterway, or a little over 60 percent of total tonnage.

About 5 percent of global shipping crosses through the Panama Canal.