UPDATE 1-Australia mine tax revenue $60 bln less than planned

* PM Gillard rules out major changes to tax deal

* Tax laws due in May (Adds Gillard, Greens comments)

SYDNEY, Feb 16 (Reuters) - Australian Prime Minister Julia Gillard ruled out any major changes to a new mining tax on Wednesday after reports her compromise with big miners will see the tax collect up to A$60 billion ($60 billion) less than originally planned over 10 years.

Treasury figures show the original tax would have raised A$99 billion between 2012/13 and 2020/21, but the revised tax would earn A$38.5 billion, the Sydney Morning Herald and Financial Review newspapers said, quoting treasury documents.

The Australian Greens, who want the mining industry to pay higher taxes, said the figures proved the government should scrap its compromise proposal and restore the original tax plan, although Gillard was quick to reject the suggestion.

"We will deliver, through the Australian parliament, the tax as I agreed it with Australia's biggest mining companies. We will not be compromising that agreement in order to secure the legislation through," Gillard told reporters in New Zealand.

Former Prime Minister Kevin Rudd proposed the tax last year but the government watered down the tax after Gillard took over from Rudd and then reached a complex deal with big mining companies BHP Billiton , Rio Tinto and Xstrata .

The original tax was heavily opposed by mining companies and the mining industry spent millions of dollars on a public relations campaign which in part led to Rudd's fall.

Laws for the new tax are due in May, and the government will need support from the Greens to pass the legislation through the upper house Senate, where the Greens will hold the balance of power after July 1.

Australia plans to return its budget to surplus in 2012/13 and Treasurer Wayne Swan has repeatedly said that a shortfall in the mining tax revenue would not threaten the budget targets as spending would be cut in line with the revenue loss.

Swan told reporters in Brisbane that the lower revenue figures should not be a surprise, but said revenue from the new profits-based tax would remain strong.

($1 = 0.997 Australian Dollars) (Additional reporting by James Grubel in Canberra; Reporting by Narayanan Somasundaram; editing by)