Foreign Affairs Minister Simon Coveney says Ireland "cannot and will not" accept the return of a hard border.
Minister Coveney was speaking in Brussels as British and EU negotiators began detailed Brexit talks.
Following a meeting with his UK counterpart Boris Johnson, Simon Coveney said reintroducing customs checks on the border was a "non-starter".
He ruled out suggestions that a hi tech solution could resolve the issue.
"What we do not want is to pretend here that we can solve the problems of the border on the island of Ireland through technical solutions, like cameras and pre-registration and so on. That is not going to work," he said.
"Any barrier or border on the island of Ireland, in my view, risks undermining a very hard-won peace process."