Trade Minister Simon Birmingham has discussed big delays for Australian thermal coal at Chinese ports.

The slowdown in coal export was a key topic of discussion when Senator Birmingham met his counterpart in Beijing on the weekend.

Chinese authorities say new environmental checks on coal products, not political tensions, have created delays.

“I've asked them to try to work with our authorities so that Australian businesses can better understand what those checks are and how they're being applied so that we can ensure efficiency there,” Senator Birmingham told Sky News on Sunday.

He said China may be aiming to help its domestic coal producers by putting tighter controls on imports.

“There may be some broader issues at play when it comes to China seeking to manage the volumes of thermal coal coming into the country,” Senator Birmingham said.

ABS stats show Australia sent $1.2 billion worth of coal to China in May alone - 22.3 per cent of all the coal exported that month.