Leaders of Ireland's Greens hope party members will vote on Wednesday to back a deal to enter government for the first time and swallow long-standing opposition to Irish Prime Minister Bertie Ahern.
Backing for a coalition agreement reached with Ahern's Fianna Fail party late on Tuesday would guarantee him a parliamentary majority following an inconclusive May 24 general election and secure him a third successive term.
Fianna Fail emerged largely unscathed from the election with 78 seats in the 166-seat Dail (lower house of parliament) but Ahern needed new allies after his pro-business junior coalition partner, the Progressive Democrats (PDs), suffered big losses.
Senior Green Party officials said they expected to secure the two-thirds backing of their members required to enter a coalition government having won what they said were significant policy concessions in return for backing Ahern.
Green Party negotiator Dan Boyle cautioned, however, that his powers of persuasion had been limited by the fact that Ahern could probably have secured a wafer thin majority even without the Greens and their small number of seats. "The six party seats, while useful, weren't necessarily needed," he told state broadcaster RTE.
Ahern is expected to keep the two remaining PD lawmakers as partners and bring on board four independents which, together with the Greens, would give him the backing of 90 lawmakers when the Dail votes on a post-election prime minister on Thursday.
All sides kept the programme for government agreed between Fianna Fail and the Greens under wraps until members had seen it but The Irish Times reported Ahern had agreed to introduce a carbon tax during the lifetime of the next government.
The Greens had also secured extra funding for education but had dropped opposition to Fianna Fail's plans to cut income tax and to the use of Irish airports by US military flights bound for Iraq, the newspaper reported.
As a compromise Ahern has agreed military flights in and out of traditionally neutral Ireland that are not operating under a United Nations mandate will, in future, need Dail approval.
A Green Party convention is due to start in Dublin at 3 pm (1400 GMT) but a vote is unlikely to take place before the evening. Party leaders believe the recent involvement of fellow greens in governments in Germany and Finland will help persuade members to put them in power in Ireland for the first time.