Taoiseach Enda Kenny has appealed to junior doctors to call off their strike to prevent patients from suffering.
Fifty-one hospitals have been hit by the walk-out by 3,000 non-consultant hospital doctors (NCHDs) over long working hours with pickets placed outside at least eight hospitals.
Mr Kenny said that it should be possible for the doctors to go back to the Labour Relations Commission (LRC) to sort out the dispute.
"The first thing is that this strike should end. It's absolutely critical that the LRC be able to engage with HSE and the NCHDs on this matter," he said.
Mr Kenny said that the only people who were suffering in the dispute were patients who had operations cancelled due to dispute.
"I met two yesterday who had been fasting all day waiting and now it's called off," he said.
About 12,000 outpatient appointments have been cancelled as a result and about 3,000 operations have had to be postponed.
It came after Independent TD Stephen Donnelly called for binding sanctions on the HSE if it did not end shifts lasting up to 36 hours for junior doctors.