SIPTU is to ballot union members over pay from December 1st
The Fianna Fáil leader Michael Martin says the provision of services has to be put before any increases in public sector pay.
He says there are huge economic challenges and the country cannot afford a new agreement outside of Lansdowne Road.
SIPTU is to ballot union members for industrial action and strike action on public service pay from December 1st.
Pressure is building on the Government to set a date for public salary negotiations, since the recent deal negotiated with gardaí.
But Mr Martin told Newstalk Breakfast that now is not the right time.
"You throw Brexit in, it's the most fundamental structural change to our economy in over 45 years - and it is frightening in terms of its potential impact on the country".
"Therefore is it not time for all of us - this isn't about ideology, this is about being honest with people - and saying 'we're still borrowing to do what we're doing, is it not time for all of us ton stand back and say isn't it time to be cautious now".
"We're saying without question that we cannot undermine or reduce the amount of money that's available for vital services."
Asked if his party would pull its support from Government if they do not support Lansdowne Road, he said: "We're not looking at this in the context of a general election, at all".
"It's not about sowing more instability or trying to undermine the immediate situation in terms of Government...but we are keeping, obviously, a watching brief on this.
"And we were somewhat annoyed that about two to three weeks ago the unwinding of Lansdowne began without any consultation with us at that particular time".