Greens leader Christine Milne is hoping to meet key crossbench senators to try to save the renewable energy target.
Senator Milne has requested meetings this week with RET fence-sitters Jacqui Lambie, Nick Xenophon and Ricky Muir. She has penned personalised letters detailing the impact of a target scale-back.
The government wants to slash the target of 41,000 gigawatt hours to about 27,000. It claims that figure represents 27 per cent of energy use by 2020 instead of the bipartisan level of 20 per cent.
After major party talks failed, crossbench senators developed a plan to include existing hydro and solar power in the target - avoiding the need for new investment in the sector.
They need six crossbench senators to back the plan if the government signs on.
The Greens say the proposal will cost billions in investment and do nothing to reduce emissions.