TEHRAN, Young Journalists Club (YJC) - The EU needed to be well prepared for everything, Barnier said, telling German broadcaster Deutschlandfunk: "That includes the no-deal scenario."
He said the issue of the Irish border with Northern Ireland was "the most sensitive point" of the negotiations. Of a solution to the issue, he added: "I think that is possible."
On Wednesday, Barnier said the EU is prepared to offer Britain an unprecedentedly close relationship after it quits the bloc but would not allow anything that weakened the body's single market.
He reiterated that point in the Deutschlandfunk interview, saying the EU's offer of a "unique partnership ... should not be at the expense of what we are."
With seven months to go until Britain is due to leave the EU, the two sides are yet to reach a divorce deal. Officials increasingly expect an informal October deadline to slip into November.
Britain's Brexit minister Dominic Raab told lawmakers on Wednesday he was confident that a deal was "within our sights", although he added that there was "some measure of leeway" on the October timetable.