British Prime Minister Boris Johnson and the head of the EU’s executive, Ursula von der Leyen, have agreed to step up Brexit talks to close “significant gaps” barring a new trade partnership.

The two sides have said last week’s round of talks aimed at getting a new, post-Brexit trade agreement from 2021 made some progress but did not yield a breakthrough.

The EU says a deal must be sealed by the end of the month, or the first days of November at the latest, to leave enough time for ratification in the bloc by the end of the year.

Johnson and Von der Leyen discussed the next steps in a phone call on Saturday.

“They agreed on the importance of finding an agreement, if at all possible, as a strong basis for a strategic EU-UK relationship in future,” they said in a joint statement. “Progress had been made in recent weeks but … significant gaps remained, notably but not only in the areas of fisheries, the level playing field and governance.”

The two leaders instructed their Brexit negotiators, Michel Barnier and David Frost, “to work intensively in order to try to bridge those gaps”.

Johnson said earlier on Saturday that the UK continued to push for a Canada-style deal with the EU, but was also ready to sever existing close-knit trade ties and default to general World Trade Organization rules, which include quotas and tariffs.

“I think there’s a good deal to be done,” he said. “There’s a big opportunity for both sides to do well.”

More trade talks are due in London next week and in Brussels the week after before the 27 national EU leaders meet on October 15-16 to assess progress. London has also said it wants clarity by October 15 on whether a deal is possible or not.

An estimated €1-trillion worth of annual trade would be at stake if they fail to get an agreement.

The EU says it will not implement any new deal if London undermines their earlier Brexit divorce treaty with its draft Internal Market Bill.

With time running out, controversy over the ruling Conservative Party’s proposed new UK law has cast fresh doubt on whether a deal is possible, but German Chancellor Angela Merkel said on Friday she was still “optimistic”.

The EU says the British government is split between hawks like Johnson aide Dominic Cummings, architect of the 2016 leave campaign, and those Brussels depicts as more moderate like UK negotiator David Frost on whether to push for a deal or leave without one.

British foreign minister Dominic Raab said on Saturday that the EU no longer had the power to treat Britain poorly.

“Yes, we want a free-trade deal with the EU, but any deal must be fair. The days of being held over a barrel by Brussels are long gone,” Raab said at the Conservative Party’s annual conference.