Steven Rockefeller's warning comes as ABC Radio reported a rift between Australian Greens leader Senator Bob Brown and Tasmanian Greens leader Nick McKim over the six-month moratorium on the logging of high conservation value forests.

But Mr McKim said in Hobart yesterday that there was no split.

"We both think the statement of principles that had a three-month process to implement the moratorium has not been, and will not be, met," he said.

"We remain optimistic that the process now under way will lead to the protection of our high conservation value forests.

"It's disappointing that the original moratorium won't be met, but we call on all parties to implement the full moratorium as soon as possible."

Senator Brown was more blunt, saying yesterday that the deal was a breach of public trust in the forest principles process.

"Mr Kelty says, `Let me place on record our appreciation of Bob Gordon and Forestry Tasmania for your support in this difficult process', (but) no mention of environmentalists," Senator Brown said.

"Mr Gordon says Mr Kelty believes an agreement may be possible, if a proposed pulp mill at Bell Bay proceeds, and to add insult to injury adds that, by necessity, some coupes in the area proposed ... for reservation will be logged over the next six months.

"That is, the proposed moratorium has been dumped."

Mr Rockefeller is a trustee of the billion-dollar Rockefeller Brothers Fund, which in 2005 donated $US200,000 to a campaign to protect Tasmania's forests.

Mr Rockefeller said if Gunns was to back away from sustainable forestry it would be a "major setback" for Tasmania and "irresponsible", leading to "renewed protests by well organised, international advocacy groups". Rockefeller Brothers' fund manager Michael Northrop said that Tasmania had scored a huge victory with Gunns' decisions on sustainable logging and it would be a "significant step backwards to reverse course".