Greens leader Bob Brown has guaranteed carbon price legislation will not be repealed despite promises from Opposition Leader Tony Abbott that he would "oppose it in opposition and rescind it in government".

Senator Brown predicts an agreement on a climate legislation is only about two weeks away - but says it is not going to be a "green outcome".

The Greens will have the balance of power in the Senate from Friday and Senator Brown says his party will not support any rescission motion - even if the Coalition is in government.

"I can give you a rolled gold guarantee that when and if this package, after all this work on behalf of the Australian people passes our parliament, we will be giving it every guarantee for the future," Senator Brown told the National Press Club.

"Of course we won't be supporting a rescission motion by Tony Abbott. This is, of course, central to the Greens.

"While ever we are drawing breath in the Senate we will defend the outcome - unless it can be improved."

Earlier, independent member of the multi-party climate change committee Rob Oakeshott detailed the matters still to be thrashed out between the Government, Greens and independents.

Mr Oakeshott said the sticking points are compensation for polluting industries, which rely on exports, compensation for households, and how much of the carbon tax should be funnelled into renewable energy projects.

He forecasts that an agreement is only "a week or two away", and Senator Brown agrees.

"I remain confident that we, Labor and the independents can achieve an agreement to tackle global warming in the next couple of weeks," Senator Brown said.

Asked if the Greens wanted the emissions target to be more than the Government's policy of a 5 per cent reduction from 2000 levels by 2020, Senator Brown indicated resistance in the committee to change.

"If you say there's an immovable object and an irresistible force here so it has seemed to be, but we're all working together, there is give and take - there has to be," he said.

"This is not going to be a green outcome."

He said that the Greens' target has been similar to world targets of 25 to 40 per cent reduction in emissions.

"But if you are looking for that in the outcome you are going to need a pair of binoculars," he said.

Senator Brown was also forced to defend his opposition to land buy ups in northern New South Wales by Chinese mining company Shenhua, saying the powers of the Foreign Investment Review Board (FIRB) should be reviewed.

He said FIRB only looks at foreign investments of more than $231 million, so there is no scrutiny of the property purchases like those near Gunnedah.

"[There is] the potential loss of that magnificent food producing country in an age where food resources are critical," he said.

Senator Brown also used his Press Club address to release research that put foreign ownership of Australia's mining companies at 83 per cent, in a bid to extract a more lucrative mining tax from them.

But Prime Minister Julia Gillard says she has worked with miners to develop the tax, and it will not be changed.

"The draft legislation is now out there for further feedback from Australia's miners and I am determined that we will legislate the Minerals Resource Rent Tax as I shaped it in my first few days as prime minister," Ms Gillard said.