The INMO will announce details later of the first of a series of 24-hour strikes by members.
It comes after nurses and midwives voted overwhelmingly in favour of strike action last month:
In December, 95% of INMO nurses and midwives voted to go on strike in a dispute over staff shortages and pay.
Later today, the union's executive council will meet to discuss the result and decide on the next steps.
Afterwards, the union says it will announce the dates of the first in a series of 24-hour national strikes.
A previous nurses protest in September last year. Pic: Press 22
The action will see INMO members withdraw their labour, providing only emergency and lifesaving care.
The union says that the low levels of pay mean the public health service is unable to recruit and retain enough nurses and midwives to safely care for patients.
Pay proposals by the Government were rejected by INMO members as insufficient in October, the union saying that most nurses and midwives would not have seen the proposal's benefits.
If strike action goes ahead, it would be only the second time INMO members have taken the action - the last time being 1999.
