(Adds AGL, politicians' and market operator comments) Sept 6...

(Adds AGL, politicians' and market operator comments)

Sept 6 (Reuters) - AGL Energy (AGL), Australia's biggest power generator, came under pressure from the government on Wednesday to sell rather than close one of its coal-fired plants in 2022 to help keep the lights on in a market short on stable power supplies.

The company said it remained committed to shutting its Liddell power station in 2022, even after Prime Minister Malcolm Turnbull said the government was talking to AGL Chief Executive Andy Vesey about selling the plant.

"AGL has committed to the closure of the Liddell power station in 2022, which is the end of its operating life," AGL said in a statement.

The comments came after the Australian Energy Market Operator warned this week of a heightened risk of blackouts in Australia's most populous state, New South Wales, after 2022 if Liddell is shut.

The clash between the government and AGL highlights challenges facing Australia, where blackouts have become more frequent following a decade of uncertainty over carbon policy that has deterred investment in stable generation to back up wind and solar power.

Turnbull told parliament on Tuesday that he was talking to AGL about extending the life of the Liddell plant for at least five years, and later told reporters that CEO Vesey was willing to consider selling the plant.

"He's said that he would be prepared to discuss selling to a responsible party who would be able to keep the power station going for a period," Turnbull said.

AGL said early on Wednesday it still plans to close the plant in 2022, noting that it had given the market seven years notice on its plans in order to allow time for investments to replace that capacity.

"Keeping old coal plants open won't deliver the reliable, affordable energy our customers need," Vesey said on social media.

The company said it continued to assess the capacity that would be needed after 2022 to replace Liddell.

"AGL will continue to engage with governments, regulators and other stakeholders to deliver appropriate outcomes but notes that the company has made no commitment to sell the Liddell Power Station nor to extend its life beyond 2022," the company said.

Energy Minister Josh Frydenberg said on Wednesday it was too early to say how much it would cost to keep Liddell open or whether it would involve government funding.