Speculation is rife that a carbon tax deal is just around the corner, with the ABC reporting a deal could be finalised between the government and Greens in the next week-and-a-half.
The Australian Greens say they will deny Opposition Leader Tony Abbott a mandate to scrap the carbon tax if the coalition wins the next federal election.
On Thursday morning, Greens leader Bob Brown said there was still work to do.
"We're not there yet," he told ABC Radio on Thursday, following formal meetings of the committee on Tuesday and Wednesday.
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"We have crossed a couple of major hurdles which were there last week, but we still haven't crossed the lot."
Senator Brown says he's giving a rolled gold guarantee that his party, which will hold the Senate balance of power from July 1, will stop Mr Abbott from doing so, even if it means a fresh election.
Under the constitution legislation that is rejected or amended by the Senate can be used as a trigger for a double-dissolution election.
The Greens, independents and Labor, are close to an agreement on carbon pricing, with some suggestions the package could be released as early as next week and legislation to go to parliament in September.
One of the hurdles crossed was a firm start date for an emissions trading scheme.
The government reportedly will guarantee that a carbon tax, due to start on July 1, 2012, will switch to an emissions trading scheme in 2015.
The move is a bid to calm business concerns about an uncertain transition and appease voters angry about Prime Minister Julia Gillard's "no carbon tax" broken election promise.
The Greens will support a 2015 start date for an ETS.
"We've said three to five years, it comes within that range," Senator Brown said.
