Fianna Fáil says it will consider its support for Fine Gael "one budget at a time".
Fianna Fáil leader Micheál Martin has said he still does not believe the country will be able to afford scrapping the Universal Social Charge.
Earlier, the Finance Minister Michael Noonan told TDs he still believed the charge could be phased out over five years.
Asked if Fianna Fáil would veto the plan, Micheál Martin said it would consider the plans put in front of it, adding: "We need to keep a balance making sure we can invest in the infrastructure of the country and also give people a break.
"(Abolishing the USC) is not a position we agree with…We'll take it one budget at a time."