Ireland "may have to live" with a no-deal Brexit for a period of time, Leo Vardkar has said.
Speaking in Stockholm the Irish prime minister said his country would "do what is necessary to protect the single market".
He also suggested that the Irish government would enforce some kind of border controls in the event of a no-deal, while an agreement was being negotiated with the UK.
"I think what I've said before is that if we end up in a no-deal scenario, it may be the case that we have to live no-deal for a period of time," the Taoiseach said.
"Ireland will do what is necessary to protect the single market, to ensure our place in the single market is protected - it protects our jobs and our economy, and our prosperity.
"But having to do that for a period of time while we negotiate a deal or pursue other solutions is very different to an Irish government actually signing up in an international treaty to put in place checks between North and South. That's something that we can't countenance."
Mr Varadkar said that while no-deal preparations were "extremely advanced" and that its ports were ready for customs checks, it had not yet agreed how contingency plans for the land border with the UK would work.
"We will of course want to protect the single market, because we're going to stay in the single market no matter what happens. But we haven't yet agreed contingencies with the European Commission on how that will be managed," he told reporters.
The Taoiseach said the upcoming Irish budget would be a "no-deal" budget and include rescue packages for businesses that could be affected by problems at the border caused by British policies.
His comments come as EU opposition to a border proposals presented by Boris Johnson on Wednesday mount. Mr Varadkar himself said the plans "fall short" of what was needed.
Meanwhile his deputy Simon Coveney said there were aspects of the proposals that Ireland "couldn't possibly support", while the European Commission branded the proposals "problematic" and said the onus was on the UK to fix them.
Donald Tusk, the European Council president, said member states were open to improvements but were so far "not convinced".
