Ursula von der Leyen has started to 'lean on' Michel Barnier to strike a post-Brexit trade deal with the UK amid rising hopes the outline of an accord could be in place by the end of the week.
Mr Barnier, the EU's chief negotiator, is locked in talks with UK counterpart Lord Frost, but formal discussions remain deadlocked on a handful of crunch issues.
However, Ms von der Leyen, the President of the European Commission, is said to be putting the pressure on Mr Barnier to find a way through the stalemate.
UK sources said Ms von der Leyen is now being 'quite helpful' and is 'keen to unblock things'.
However, despite more activity on the EU side, Number 10 has cautioned that the chances of the two sides splitting without an agreement next month may be 'underpriced'.
Ursula von der Leyen, the President of the European Commission, has started to 'lean on' Michel Barnier to strike a trade deal with the UK
Mr Barnier arrived in London on Friday to resume face-to-face talks with UK counterpart Lord Frost
The post-Brexit 'standstill' transition period is due to end in December but the path to a trade deal remains blocked by three key issues: Fishing rights, the so-called 'level-playing field' on rules, and the future governance of the accord.
Face-to-face talks between Mr Barnier and Lord Frost resumed yesterday after they had to be suspended after a member of the EU team tested positive for coronavirus.
The latest round of talks has been billed as potentially the final set of discussions as the clock ticks down to the end of the transition period.
Mr Barnier's negotiating mandate is set by EU leaders but the Sunday Times reported that Ms von der Leyen has started to 'lean on' him to make progress and get a deal done.
One senior British official told the newspaper: 'Von der Leyen has been quite helpful.
'She is keen to unblock things. Her team has been more involved of late which is helpful.
'On the level playing field and state aid we aren't there yet but we can see how we get there. The problem is fish.'
In a sign of the European Commission's growing involvement in the talks, Ms von der Leyen has sent Stephanie Riso, one of her most senior officials, to help Mr Barnier.
Ms Riso was involved in the original Brexit divorce negotiations and is viewed as someone who could help break the deadlock.
It is thought Boris Johnson could speak to Ms von der Leyen in the next 48 hours to try to hammer out a way forward on fishing rights, arguably the biggest remaining point of contention.
He may also speak to French President Emmanuel Macron who is adamant the EU should stick to its tough stance on the issue.
Both sides now believe that if a deal is possible it will have come into view by the end of this week.
But Number 10 has warned that there is still a 'significant gap' on fisheries and 'no deal is arguably underpriced'.
Reports last week suggested that Mr Barnier recently said the EU could accept a 15-18 per cent cut in its share of fishing rights in UK waters, but British officials immediately rejected the offer.
Boris Johnson is expected to speak to Ms von der Leyen in the next 48 hours as the two sides try to facilitate a breakthrough
A Government source said: 'These figures are risible, and the EU side know full well that we would never accept this.
'There seems to be a failure from the Commission to internalise the scale of change needed as we become an independent nation.'
The Government has repeatedly said it is prepared to leave the transition period without a deal if the EU fails to move.
A UK source close to the negotiations said: 'Over the coming days we will continue to negotiate with creativity and intensity.
'We hope that the EU will come with some fresh thinking because what we've seen so far doesn't cut it. They must understand that we are not going to sell out our sovereignty.'