The talks on the unions' claim for early retirement from 50 were expected to continue right up to the annual round of teachers' conferences, starting on Easter Monday.
Early retirement has for some years been the unions' priority. Niamh Bhreathnach, minister for education, gave a general commitment to introducing a scheme two years ago, but now negotiations have come to a head.
If the talks fail, widespread industrial action is likely, as tough motions have been tabled at all three conferences.
The department of education is willing to permit early retirement for teachers who are "unable to perform to the best of their abilities" - a reference to problem teachers, but a red rag to the unions, which say their members would be stigmatised if they accepted early retirement in this way.
The department is also prepared to concede early retirement to teachers who become surplus to requirements through falling enrolments. But it has resisted the claim for a general retirement scheme.
The department of finance is determined to limit the scope and cost of any scheme. It is particularly concerned at the knock-on effects of a deal on other groups, most notably the nurses who also want an early retirement scheme. It is also worried about the implications for the national pension bill in the next century, when Ireland's aged population will have greatly increased.
Earlier this year, the government came up with an offer of retirement at 55 years, after 35 years of service. The Irish National Teachers' Organisation walked out of talks in protest, as its members already enjoy these conditions.
The two secondary unions, the Association of Secondary Teachers, Ireland and the Teachers' Union of Ireland, also rejected the offer, although it does represent an improvement on the current retirement age of 60 years for secondary teachers. However, both unions point out that most of their members would be well over 55 by the time they had 35 years of service.