David Cameron is to urge big business to get behind his EU renegotiation as he embarks on a three-day diplomatic offensive at the World Economic Forum.
The Prime Minister will hold discussions with political and corporate leaders at the annual gathering in the Swiss ski resort of Davos as he fights to secure a deal at a summit next month.
But the prospects of a swift deal were played down by French Prime Minister Manuel Valls, who said the negotiations had "only just begun" and warned that a deal "at any price" would not be acceptable.
Mark Rutte of the Netherlands and Luxembourg's Xavier Bettel are among the politicians Mr Cameron is due to meet ahead of a summit next month where he hopes to finalise a reform package to put to UK voters in an in/out referendum.
Discussions however are also likely to be dominated by urgent efforts to deal with the growing migrant crisis - with the UK vowing to oppose any move to axe rules requiring refugees to claim asylum in the first EU country they enter.
Member states have been warned the Schengen passport-free travel zone will collapse if action is not agreed within two months as 2,000 migrants are still arriving daily - and scrapping the so-called Dublin regulation is among ideas being floated.
Mr Cameron still hopes to secure a deal to persuade voters not to back "Brexit" at a Brussels summit on February 18 - to allow an in/out referendum to be held in June, before the flow of refugees increases again in the spring.
Asked if he believed that could happen, Mr Valls told reporters in Davos: "No, I think it will need more time. The discussions have only just begun."
He said it would be "undoubtedly a bad thing, a very bad thing" for the UK to leave and France wanted to find a resolution "but not at any price".
Mr Cameron will use his speech in Davos to attempt to switch focus from his attempts to win support for benefit curbs on EU migrant workers and on to efforts to cut Brussels red tape - another of the four stated aims of the renegotiation.
Banking giant Goldman Sachs was reported by Sky News to have donated a "substantial six-figure sum" to pro-EU campaign group Britain Stronger In Europe.
Zhu Min, deputy managing director at the IMF, said it was "very difficult to see the financial and economic situation" for Brexit.
He told the BBC Radio 4 Today programme: "In the past 10, 15 years all we talk about is globalisation. Interconnectivities have become such a big thing, we are all closely linked to each other. So, it's really hard to see someone want to isolate itself."
Downing Street said a Cabinet meeting will be held "soon after" the conclusion of negotiations to agree the Government's position on the deal obtained by Mr Cameron, but declined to be drawn on the possible timing.
Cabinet's regular weekly meeting at Downing Street is on Tuesday, potentially leaving three full days - if a deal is reached at the summit - during which the PM could trumpet the success of his negotiation while Eurosceptic ministers remain gagged.
A Downing Street source said: "The Prime Minister has said there will be a Cabinet meeting. That will take place soon after any deal has been reached."
The source declined to say whether that could mean the meeting being brought forward to Friday evening or Saturday, saying: "We are not setting out timetables. We are still in negotiations - we haven't got a deal."