Yancoal Australia asked the Foreign Investment Review Board to either delay or lower the level of its interest in coal mining in New South Wales and Queensland.

The Chinese-owned firm promised to float at least 30 per cent of the company on the Australian Stock Exchange by 2012. It made the promise in 2009 when it purchased Felix Resources for $3.5 billion.

In December, Yancoal signed a merger proposal with Gloucester Coal, which has mines in NSW's Gloucester Basin and Queensland's Bowen Basin region. Gloucester is 64 per cent owned by the Noble Group, based in Hong Kong.

The FIRB initially told Yancoal, owned by China-based Yanzhou Coal Mining, to instead reduce its interest in the $3.5 billion purchase of Felix Resources if it wants to go ahead with its $8-billion takeover of Gloucester.

Yancoal cited weakening economic conditions are the reasons behind its request to waive some of its 2009 promises.