Fianna Fáil have said they will not pass the Budget just for the sake of it.
It is the last one of the Confidence and Supply agreement between Fianna Fáil and Fine Gael.
However, they said there is not as much money available to be spent as they thought heading into negotiations.
Deputy Michael McGrath said Finance Minister Paschal Donohoe may not have been aware of the situation until recently, but warned that he should have been.
He said: “That is certainly an issue and it makes it challenging for us to ensure that we can get the best possible outcome for the country and the people that we represent.”
He also warned The Government has less than the €700m needed for the country to "stand still" next year in its imminent budget 2020 plans.
The opposition party's budget negotiators criticised the "slow" progress of the ongoing talks with Finance Minister Paschal Donohoe - warning that they are "less advanced" than in previous years.
The party's finance spokesman, Michael McGrath, and public expenditure spokesman, Barry Cowen, said problems persist in the talks. While saying that progress has been made in some areas, they said the negotiations have faced significant delays and that the money available for new services is "very, very limited".
"The information given to date is that we're looking at an overall budget of around €2.8bn, of which €2.1bn was pre-committed, leaving headroom of about €700m for package of budgetary decision. But it seems to us that when the Minister for Finance gets into discussions with the various departments the picture is very different indeed.
"The headroom for new measures is very, very limited," Mr McGrath said.
Mr McGrath said Fianna Fáil is trying to ensure that any money raised from carbon tax increases will be ring-fenced to provide funding for related projects including home insulation schemes.
However, he and Mr Cowen repeatedly declined to go into exactly how much they believe the carbon tax rate will increase by in next Tuesday's budget plans, amid suggestions Fine Gael wants to raise it by €10 and that Fianna Fáil wants to limit any increase to between €5 and €7.
Mr Cowen also said it is vital that the agriculture, business and trade sectors are properly protected if a no deal Brexit strikes, with Mr McGrath saying it is worrying that exact protections are yet to be fully implemented.
Asked if there is still scope for some tax changes, Mr Cowen said changes could still take place. However, he emphasised that the priority must be on services for the public.
Mr McGrath added that the party went into the coalition for the "greater good".
He said: “We are here today; we are available all weekend, we are available on Monday just to continue with it.
“We have done our business professionally in a business-like manner without any drama.
The party said it is not issuing any threats or red lines to the Government over next week’s budget
He said this year’s negotiations have been more difficult than previous years – as the uncertainty over Brexit meant they started later than usual which undermined his party’s ability to push for the policies it wanted.
He said: “We are not trying to issue any threats or red lines.
“We know the importance for Ireland of getting through this budget. The consequences [of failing to reach an agreement], let’s be clear about it, would be a General Election – probably in early November.”
- Additional reporting by Digital Desk