European leaders have pledged to do what they can to make sure David Cameron can support Britain's continued future in the EU in a referendum expected this year.

Dutch prime minister Mark Rutte, whose country currently holds the rotating presidency of the 28-nation bloc, said he is "fairly optimistic" a deal with Britain will emerge in February, but that he is "not absolutely sure".

Addressing a panel at the World Economic Forum at the Swiss ski resort of Davos, Mr Rutte voiced his strong support for Britain's continued membership of the EU as the country is outward-looking and trade-oriented.

Mr Cameron is seeking a series of reforms on things such as benefits, powers for national parliaments and movement of people.

The Prime Minister has voiced his hope that a successful renegotiation will lead to the British people backing Britain's future in the EU in the referendum.

French prime minister Manuel Valls said it would be a "tragedy" if Britain left the EU - the so-called Brexit.