Federal Labor's mining tax is on the table for debate next week but is not yet a done deal as talks with crossbench independent MPs continue, Treasurer Wayne Swan says.
Under the proposed Minerals Resources Rent Tax, coal and iron ore output will be taxed by 30 per cent and the proceeds will be used to boost workers' superannuation and fund small business tax cuts.
Mr Swan said he was confident the package of bills, which would take effect from July 1, would be successful.
"But I don't assume it as being a done thing," the treasurer told ABC radio on Thursday.
"We're going to do our best to get it through because it's absolutely critical to spreading opportunity right across our country, maximising the benefits of the resources boom and spreading them right around to every corner."
Independent MP Tony Windsor has said he would support the tax if the government agreed to provide hundreds of millions of dollars to fund scientific studies into the impact of coal seam gas projects on sensitive farmland in the Darling Downs in Queensland.
West Australian Nationals MP and crossbencher Tony Crook has signalled he would move amendments to the bills in an attempt to make them fairer.
Mr Swan said talks with the independent MPs and minor parties on the issue were continuing.
"We'll continue to do that and hopefully we'll secure their support when the bill comes to the parliament because it's a really important reform for the long term.
"And of course if it's not put in place then what's endangered is that big boost to superannuation for millions and millions of Australian workers and of course that tax cut for small business."
If the bills pass the lower house they are likely to be supported by the Australian Greens in the Senate despite calls by the minor party's leader Bob Brown, who wants the tax to be broadened to cover uranium.
Senator Brown said he was in talks with his party colleagues on moving an amendment to include not just coal and iron ore but uranium, following the government's reversal on exporting yellowcake to India.
Labor has long opposed India being able to buy Australian uranium because it is not a signatory to the nuclear non-proliferation treaty.
But Prime Minister Julia Gillard says other global safeguards could be put in place to ensure Australian uranium is not used for nuclear weapons.
"It seems logical to me, in an age where health care and public education are short of funds right around this country, should we not be taxing the largely foreign ownership of our uranium mines?" Senator Brown said.
"We will be looking at adding that amendment in the light of the huge change that we are seeing not just in the promotion of uranium to India by Prime Minister Julia Gillard but with the uranium prices going up."
