European Union (EU) leaders on Thursday called on Britain to make necessary moves so that the two sides can reach an agreement on their future partnership supposed to start in 2021.

According to a press release issued following the first part of the EU summit in Brussels, the European Council "notes with concern that progress on the key issues of interest to the Union is still not sufficient for an agreement to be reached" before the transition period ends on Dec. 31.

European Council President Charles Michel told a press conference that the bloc remained united and determined to reach an agreement with Britain, "but not at any cost."

"Any agreement on our future relationship would have to be based on our mandate, in particular, when it comes to the level playing field, fisheries and governance," Michel said, adding the EU's chief negotiator Michel Barnier was fully trusted to continue the negotiation.

Appearing at the press conference with Michel, Barnier was certain there is a good chance of reaching an agreement.

"We're on the verge of actually finalizing the agreement on those points, but there are other areas where there aren't just question marks, but real differences, and then three subject areas where the gap is too big at the moment," he said.

British Prime Minister Boris Johnson had put a deadline of Oct. 15 for the post-Brexit deal to be reached, but Barnier defied the call, saying the EU would work "until the last possible day."

"The negotiations aren't over. We want to give these negotiations every chance of being successful that we secure an agreement," he said when replying to a media question, adding that he was prepared to speed up the next round in London.

"That's what I have proposed to the British team to negotiate the short space of time still left to us so that we can negotiate this agreement through to the end of October," Barnier said.

As for the Internal Market Bill tabled by the British government, the European Council said the Withdrawal Agreement reached in January this year must be "fully and timely implemented."

The EU had insisted that the controversial parts of the bill that may partially breach the Withdrawal Agreement be annulled, a demand rebuffed by London.

Meanwhile, the European Council also called upon EU stakeholders to ramp up preparation for all possible outcomes, including a no-deal scenario. Enditem