British Prime Minister Boris Johnson and EU chief Ursula von der Leyen on Saturday asked their negotiators to "work intensively" to overcome differences to secure a post-Brexit free trade deal.
The two leaders spoke via video-link after the last of nine scheduled rounds of talks between London and Brussels ended Friday with both sides saying significant obstacles to an agreement remained.
The intervention by the pair, who last held Brexit talks in June, is seen as crucial to finding a breakthrough in the stalled negotiations, with time running short to ratify a deal by an end of the year deadline.
Britain is due to end nearly five decades of economic and political integration on December 31, and fears are growing of travel and trade chaos if an agreement is not struck.
Johnson's office said in a statement that both leaders had "agreed to speak on a regular basis on this issue" as their teams try to find compromises for the thorniest issues.
"They endorsed the assessment of both chief negotiators that progress had been made in recent weeks but that significant gaps remained," a Downing Street spokesman said, adding fisheries, so-called level playing field provisions and governance issues were proving most problematic.
"They instructed their chief negotiators to work intensively in order to try to bridge those gaps."
Britain formally left the European Union in January but has remained bound by most of the bloc's rules during a transition phase that ends on December 31.
Both sides have pinpointed a European summit on October 15 as the latest an agreement could be reached for it to be ratified in time for it take effect by then.
Britain's head negotiator David Frost promptly said on Twitter: "That work begins as soon as we can next week."
- 'Good deal' -
However, neither London nor Brussels appear ready to make a big shift in their entrenched positions.
Johnson -- a key figure in the lengthy and divisive process to take Britain out of the bloc -- said Saturday there was a "good deal to be done" but that it was down to the EU to show more flexibility.
He added Britain was preparing for a possible a no-deal Brexit and "could make it work very well".
Meanwhile an EU source told AFP the bloc was waiting for the British "to really start negotiating on the big issues".
German Chancellor Angela Merkel, who meets the bloc's Chief Negotiator Michel Barnier on Monday, said on Friday she believed a deal was still possible, though warned the next days were crucial.
Britain and Europe have so far found no way to overcome fundamental disagreements over how to assign future fishing rights in UK waters and how to maintain a level playing field in business and state subsidy regulations.
Diplomats say the British side has been pushing for the negotiations to head into a "tunnel" -- diplomatic jargon for a closed door, secretive dash to the finish line, allowing negotiators to make concessions without public pressure.
But European officials say the time is not right, as they are yet to be convinced that Johnson can be trusted to budge.
The bloc this week launched legal action in response to the UK government's attempt to overturn parts of the Brexit withdrawal deal agreed last year.
On Tuesday, British MPs backed a bill to regulate Britain's internal market from January 1, when the country leaves the EU single market and customs union.
Johnson has pushed on with the legislation despite concerns in his own party and a warning from Washington that it puts Irish peace at risk.