Fine Gael and Fianna Fáil have stopped short of committing to a 7 per cent annual reduction in carbon emissions.
Leo Varadkar and Micheál Martin wrote to the Green Party leader Eamon Ryan inviting him to have further talks on the matter.
The reduction in emissions is a red line for the Greens if they are to enter government.
Fine Gael and Fianna Fáil have said considerable work would have to be done to spell out how the reduction would be achieved.
Green Party TDs and Senators have been considering the response from the two leaders this morning.
