EU chief Brexit negotiator Michel Barnier | Emmanuel Dunand/AFP via Getty Images Michel Barnier: EU-UK trade deal could take 3 years The EU’s chief Brexit negotiator also says he plans to step down from his role in 2019.

A trade deal between the EU and U.K. would take three years to negotiate and may unravel, the bloc's chief Brexit negotiator Michel Barnier warned in an interview with Belgian newspaper De Tijd published today.

Asked whether trade talks could take longer than the mooted two-year transitional period after Brexit, Barnier replied: “Three years if we start talking in December. It comes with risks too, because all parliaments have to give approval [to a new deal]."

Barnier said several options for a post-Brexit trade relationship are on the table, including a Canada-like deal or something similar to the Norwegian model.

“The U.K. government said at the start of negotiations that it doesn’t want to be in the internal market and customs union. The only relationship that has no friction with the internal market is single market membership, like Norway has," he said.

He added that any future relationship between Britain and the EU comes with rights and obligations. “There is no combination possible between a free trade deal and internal market membership. Out is out.”

Barnier said British Prime Minister Theresa May's speech in Florence led to "new dynamics" in Brexit negotiations but he added: "We're still not there."

In separate comments to British newspaper the Telegraph, published Monday, Barnier said: "My team are already starting work on a draft of the treaty for the exit of the U.K. from the EU.”

He added he will step down from his role soon after Brexit day, March 29, 2019. “After that, I will see where I can still make myself useful in the EU."