Finland said Tuesday more work needed to be done on a third international bailout deal for Greece worth 85 billion euros ($94 billion).
The European Commission said Athens and its creditors had reached a technical agreement "in principle" on a bailout -- the third since 2010 -- after marathon talks stretching into the early hours.
But Finnish Finance Minister Alexander Stubb told reporters in Finland that "agreement is a big word."
"We must take one step at a time," he said, adding: "There remains work to be done with the details."
Finland is known as one of the hardliners in the eurogroup, partly due to the influence on its government of the eurosceptic Finns Party, which is part of the centre-right coalition that took office in May this year.
The party had been staunchly opposed to any new bailouts but chose to back the bailout talks in the end.
Finnish Foreign Minister Timo Soini, who is also Finns Party leader, told Bloomberg News on Saturday that Finland would end up supporting the bailout deal even though the Finns Party believes it won't solve Greece's problems.
"We should admit that this isn't going to work," he said.
But the Finns Party has no choice but to support it because not doing so would cause Finland's three-party government to collapse, he said.
"With this government structure we can't block the programme alone," he said, adding: "We'd be replaced."
Greece and its creditors -- the EU, the European Central Bank, the eurozone bailout fund and the International Monetary Fund -- are under pressure to finalise the deal by August 20 when Athens must repay some 3.4 billion euros to the ECB.
The outline for the deal comes after months of acrimonious negotiations between the creditors and Greece's radical-left government, which came to power promising an end to years of painful austerity demanded in exchange for the cash.