The Fianna Fáil leader Micheál Martin says his party and Fine Gael would 'ideally need the involvement of a third party' to form a new government.
The two parties are working to finalise a framework document for a new government, with much of it focused on how the country can recover from the effects of the COVID-19 pandemic and rebuild the economy.
It is also to look at the wider healthcare system, housing crisis and how to lower Ireland's carbon emissions.
However, the two parties are keen to win the support of smaller parties, as Fine Gael and Fianna Fáil do not have the numbers on their own for a Dáil majority.
Micheál Martin is calling on other smaller parties to read what he described as a "robust" FF/FG document.
He said: "We should be in a position to agree the document tomorrow.
"I think it's a strong document, and does point very much in the State of greater State-led intervention in areas like childcare, moving towards a single-tier health system, transforming experience of access to public and affordable housing, and also in terms of a Green New Deal.
"I would ask other parties to at least assess the document, have a look at it and engage... but that obviously is a matter for the other parties."
He said the context of the document is "restarting and rebooting" the economy, but that it will also look towards a new type of society in the future.
Deputy Martin said the two parties want a majority and a Government that will last five years.
He said: "Ideally we would need the involvement of a third party, of course."
