Fianna Fáil leader Micheál Martin is set to be elected taoiseach (Irish prime minister) at a special meeting of the Irish parliament.
On Friday, members of Fianna Fáil, Fine Gael and the Green Party backed a programme for government, paving the way for an historic coalition.
Voters went to the polls in a general election in February but no party received a majority.
Coalition talks were then halted by the coronavirus pandemic.
The two larger parties needed the support of the Greens to have a working majority in the Irish parliament (the Dáil).Hungary to finance Turkish Stream offshore to buy Russian gas