Coal loading through Newcastle is being delayed as concerns increase about Port Waratah Coal Services' ability to operate at rated capacity.

PWCS has a rated capacity of 75 million tonnes annually, but has only been able to load coal at a rate of about 67Mt.

As many as 17 ships have been at anchor in recent weeks. Late loading penalties are around $1.03 a tonne.

A logistics expert from PriceWaterhouseCoopers has been commissioned to examine coal loading in the port.