Brexit talks now require a "decision" rather than going into "extra time", the EU's chief negotiator Michel Barnier said Friday as the clock runs down on March 29 when Britain is set to leave the block, with or without an exit deal.

"We don't need extra time, what we need now is a decision and for everyone to take responsibility," Barnier told Europe 1 radio.

He did not exclude granting Britain more negotiating time - beyond March 29 - for concluding an agreement on the Brexit divorce terms, but said it was now up to "the British to take their responsibilities and assume the consequences of decisions they took democratically," he said.

The British government said Thursday that ongoing Brexit talks are focusing on securing new guarantees to reassure eurosceptic British lawmakers, rather than on demanding that a divorce deal already concluded with the EU be re-opened.

EU leaders insist the withdrawal agreement, which they struck with Britain last year, cannot be re-opened to appease British MPs who rejected it in parliament.

Brussels however appears open to adopting a more ambitious political declaration that would set a roadmap for negotiating close EU-UK trade ties during a transition period after March 29.