Management, however, held out hope that mass redundancies could be avoided, insisting that "everybody is still talking and all the balls are in the air".
Amid a deepening financial crisis, Sir Colin Southgate, chairman of the opera house, is seeking lower rates of pay for the 450 staff, which includes stage personnel and administrative staff.
He has warned that all employees would be dismissed unless they signed up to a deal which means pay cuts of up to 30 per cent for some employees.
Union leaders last night were hoping the final decision might be postponed until Wednesday when the Royal Opera House board meets.
Management is seeking to negotiate the new terms for the rebuilt Royal Opera House, due to open in December next year after a pounds 214m overhaul.
Ballet dancers in particular were being asked to agree to "dangerous" working practices, according to their union Equity.
A 12-hour working day and a 70 per cent reduction in stage staff would put dancers at risk, the union claimed.
It was "insulting nonsense" for the Royal Opera House to scapegoat its artists and staff for the problems it faced, said Ian McGarry of Equity.
A spokesman for the Musicians' Union said his members were being asked to do the same amount of work in a 40-week season as they did under the present 52-week contracts.
The technicians' union, Bectu, and the Musicians' Union have held "constructive" talks with Chris Smith, the Culture Secretary.Reuse content