June 22, 2017 - Rio Tinto has rebuffed a late offer from Glencore for its New South Wales, Australia coal operations and instead agreed to go ahead with its existing deal with China's Yancoal.

The mining giant says its board had engaged in discussion with both parties and taken the decision after considering several factors, including price and value; the risk that regulatory approvals will not be granted or significantly delayed; funding certainty; and deal execution timeline.

Earlier in June, Glencore made a $US2.55 billion ($A3.36 billion) all-cash bid for Rio subsidiary Coal and Allied Industries, which includes majority stakes in the Hunter Valley Operations and Mount Thorley Warkworth mine, a 36.5 percent interest in the Newcastle Port coal export terminal and other undeveloped coal assets.

Rio no longer views the coal operations as a core business.

It had previously agreed to a $US2.45 billion deal with Yancoal, which has already received regulatory approval.

Yancoal said, in a separate statement, it had revised its offer to make it more attractive by removing the deferred payment structure and providing further assurances on its ability to meet the timeline and secure outstanding regulatory approvals.

Yancoal, which is controlled by state-owned Chinese group Yankuang, already owns seven Australian coal mines.

"We believe Yancoal's offer to purchase our thermal coal assets for $US2.45 billion offers the best value and greater transaction certainty for shareholders," Rio chief executive Jean Sebastien Jacques said.