Irish Nurses and Midwives Organisation President Claire Mahon has said there would be an appetite for strike action among nurses if the Government imposed pay cuts.
Ms Mahon was speaking as the INMO's annual conference opened in Letterkenny, Co Donegal.
She said INMO members are feeling the strain of being short-staffed and they cannot afford to go to work and earn less.
Ms Mahon said they have reached the floor and are very willing to take action.
Vice president Geraldine Talty said that nurses are doing more than they ever did before and have hit rock bottom.
Tomorrow delegates will debate an emergency motion proposing that an alternative to Croke Part II is explored, but allowing a ballot on possible industrial action if the Government tries to impose changes without agreement.
The motion would also mandate the INMO to participate in other forms of protest action, which may be agreed with other public service unions.
The Government has given Labour Relations Commission Chief Executive Kieran Mulvey until next week to explore other proposals.
Mr Mulvey will discuss Croke Park II proposals with unions and management in an attempt to agree €300m in Exchequer spending cuts.
Earlier, INMO General Secretary Liam Doran said the union is willing to engage with Mr Mulvey, but insisted that any reforms must be proportionate and fair.
The proposed cuts under the original Croke Park II plans were disproportionate, he said.
He said it targeted half or €150m in cuts in the health sector, which made up just one third of the public payroll cost.
Mr Doran said he had no doubt that INMO members would endorse a move to mobilise and ballot for industrial action if the Government moves against them on pay.
He said members had an obligation to protect essential services and they would be doing that.
Elsewhere, Taoiseach Enda Kenny has said that the Cabinet will be briefed next Tuesday on the outcome of Mr Mulvey's talks with unions and management.