Rishi Sunak appears set to announce that the UK will rejoin the European Union’s £85 billion Horizon science research programme.
Sources familiar with the negotiations between the two sides said on Wednesday that the Prime Minister has given the go-ahead for a deal to be finalised.
The level of compensation for the UK being frozen out of the scheme during a tit-for-tat retaliation in a post-Brexit row over Northern Ireland is still thought to be an issue.
A deal could be announced within days, as first reported by Bloomberg.
One source told the PA news agency that Mr Sunak had signalled his approval of the deal but that the level of compensation for the two missed years of collaboration could still be an issue.
A conversation with European Commission president Ursula von der Leyen would be expected before the announcement.
At Prime Minister’s Questions on Wednesday, Mr Sunak told MPs his “priority and preference” was to associate with Horizon but “on terms that are right for both the British taxpayer and for British science and research”.
In a hint at a possible breakthrough, he said the Government had been “extensively involved in discussions” with the EU and “I hope to be able to conclude those successfully”.
Whitehall sources said in July that a draft deal was with the Prime Minister, prompting scientists to cautiously celebrate the development.
But Downing Street said a UK-based alternative known as Pioneer remained on the table as Mr Sunak continued to be concerned about “value for money”.
A senior scientist at London’s Francis Crick Institute welcomed the latest developments as “fantastic news” and said he would “love” for the deal to be confirmed.
Professor Robin Lovell-Badge told BBC Radio 4’s PM programme: “We’ve really been missing being able to work properly with other European scientists.
“Of course the funds would help UK science but it’s that interaction really that we’re missing so much with the rest of Europe.”
James Naismith, director of the Rosalind Franklin Institute, said: “The science community in the UK will be relieved and encouraged by this outcome.
“The Prime Minister is to be congratulated. Making the UK an attractive place for science is very important for our prosperity.”
Dame Kate Bingham, managing partner of the healthcare fund manager SV Health Investors, said: “Collaboration with the top European researchers is critical if the UK is to become a real science superpower.
“The UK bats above its weight in science and being part of Horizon means we can use that influence to drive forward world-class research to transform human progress.”
Greg Clark, chairman of the Commons Science, Innovation and Technology Committee, said: “If the news of the UK returning to Horizon Europe is true, it will be a welcome boost for both UK and EU science.
“UK science always brings a lot to international collaborations. Everyone gains from excellent UK researchers working with others to advance knowledge.”
But Labour criticised the delay, with shadow education secretary Bridget Phillipson saying: “I seriously hope that comes to pass but I do have to say what on earth have they been doing and why has it taken so long?
“This is damaging our competitiveness, it’s damaging our country and I really hope that we see progress as soon as possible.”
Horizon is a collaboration involving Europe’s leading research institutes and technology companies.
EU member states contribute funds, which are then allocated to individuals or organisations on merit.
Post-Brexit Britain continued to participate under the trade deal brokered with Brussels but was locked out during the bitter row over trading rules for Northern Ireland in 2020.