It now takes at least one month to finish customs clearance at Ganqimaodu border crossing, a much longer period compared with previous two weeks, market sources told sxcoal.com.

Impacted by this, the number of coal trucks from Mongolia to China declined sharply to 600 each day in mid-August from 1,400 in early July, and daily coal imports also plummeted to 40,000 tonnes or so from 100,000 tonnes.

Besides, trucks loaded with Mongolian coal needed to wait 2-3 days before allowed to unload at border crossings, according to a Chinese trader.

The trader said Mongolian material that declared clearance at Ceke border crossing in mid-July has not been allowed into China, resulting in a supply shortfall in the market.

How long the situation will last remains unclear. There are market talks that Ganqimaodu border crossing plans to control coal imports at around 15 million tonnes in 2017, but the current figures have exceeded 12 million tonnes, calling for tough control on imports of Mongolian coal.