VALLETTA, May 3 (Xinhua) -- Britain must make up its mind on the way forward on Brexit, the EU's chief Brexit negotiator Michel Barnier said here on Friday, insisting that a situation where the country is "neither in nor out" needed to be avoided.

Barnier was speaking at a press conference held after his meeting with Maltese Prime Minister Joseph Muscat at Castille Palace.

The EU was open to "being more ambitious in talks" if the UK wished. This, Barnier said, included the UK remaining within the EU's "customs territory".

However, he insisted that at this point a decision on the way forward could only be taken by Britain. Barnier said that the EU had engaged in negotiations with the UK without any sense of animosity or revenge.

The EU's chief negotiator refused to speculate on what might happen if an agreement is not reached by Oct. 31. He noted, however, that "the ball was now in the UK's court".

"The Withdrawal Agreement creates certainty in all areas where Brexit will cause uncertainty," Barnier said. "The Withdrawal Agreement is the only one there is."

He stressed that the EU would not compromise on its fundamental principles -- the single market, the four freedoms and the autonomy of each member state.

Muscat echoed Barnier, saying that a decision now needed to be taken by Britain on how it wished to proceed, arguing that a situation where Britain was "neither in nor out" wasn't acceptable.

The prime minister said the EU had a "good level of preparedness" for Brexit with or without a deal.