David Cameron's speech in Davos will open "a period of unprecedented uncertainty about Britain's future relationship with the European Union," according to a leading foreign affairs think tank.
The director of Chatham House, Robin Niblett, has warned the "negative impacts to UK national interests may outweigh the putative domestic political gains that [Mr Cameron's] approach is meant to deliver".
He added that hearing Cameron discuss the risks of a UK withdrawal, it "makes one wonder how a Prime Minister who prides himself on pursuing the British national interest has ended up potentially gambling those benefits away in an unpredictable EU negotiation and UK referendum process."
To the surprise of many Lib Dems, Nick Clegg appears to have played down the importance of the Coalition's divide on an in-out referendum.
Business leaders in Davos are worried about the Prime Minister's pledge to put Britain's membership of the European Union to a referendum.
With some in France keen to "roll out the red carpet" for a British exit, Germans favouring decentralisation welcome EU renegotiation talks.