Update 1pm: Ryanair is calling for the FORSA union to remove an Aer Lingus pilot it claims is interfering in the negotiation in the Irish pilot's row.
The airline says the union is being misled and is deferring to Ialpa President Captain Evan Cullen for decisions in the process which benefit Aer Lingus.
However, FORSA says its team in talks with the airline is made up solely of Ryanair pilots.
A 4th strike day is planned for next Friday and 20 Ryanair flights have been cancelled.
Speaking in Rome, Leo Varadkar says he is concerned at the escalation in tensions between the union and management.
He said: "Particularly the impact it's going to have on holidaymakers, on everyday people who have spent months saving up for their holiday who may now find themselves discommoded or rescheduled or perhaps not being able to take that holiday," he said.
Update 9.53am: Pilots union Forsa says they are ready to get back to talks with Ryanair to try to resolve the ongoing dispute.
20 flights out of 300 will be cancelled next Friday as around 100 Irish-based pilots stage a 4th day of industrial action.
It is part of a row over seniority, base transfers and annual leave.
The 3,500 passengers affected will get a refund or be accommodated on another flight.
Ryanair Spokesperson Kenny Jacobs says next Friday's cancellations will go ahead.
- Digital Desk