David Cameron will 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 within weeks.
Mark Rutte of the Netherlands and Luxembourg's Xavier Bettel are among those the PM 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.
But discussions 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.
That could leave the UK - which could engage an opt-out - and other northern European countries more open to migration flows, as the majority of refugees from Syria have been arriving in the south and trying to continue their journey overland.
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.
The pro-EU camp was boosted by a declaration by a senior aide to the Pope that the Vatican believed Britain was "better in that out".
English cleric Archbishop Paul Gallagher, effectively the Holy See's foreign secretary, told ITV News it saw Brexit "as being something that is not going to make a stronger Europe".
Mr Cameron will use a speech in Davos to attempt to switch focus from his hard-fought campaign to win support for benefit curbs on EU migrant workers and onto efforts to cut Brussels red tape - another of the four stated aims of the renegotiation.
His official spokeswoman said he would remind business leaders that "many of the reforms we are seeking are things that they have called for" in terms of improving competitiveness.
"How do we make sure that the EU - which we joined for the single market benefits and the benefits to business - continues to work for them and, indeed, work better for them," she said.
The PM will also use the event to garner backing for initiatives to create economic opportunities for Syrian migrants in neighbouring countries such as Jordan to lessen the draw of seeking a new life in Europe.
It comes ahead of a conference on Syria being staged in London next month.
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.
A spokesman for the campaign declined to be drawn on individual donations but said it was "pleased to be raising money from a wide range of sources - both large and small companies and individuals and businesses from all walks of life".
Arron Banks, the millionaire Ukip backer behind the Leave.EU group, said it would have told the bank to "stuff it" as the referendum pitted "the British people against the establishment of international bankers, multinational corporate tax dodgers and out-of-touch politicians".