British Prime Minister David Cameron predicted "ups and downs" on Friday in European Union reform negotiations but said he was determined to give Britons a proper choice on a reformed EU in a referendum he has promised before the end of 2017.

"There will be ups and downs. You'll hear one day this is possible, the next day something else is impossible," Cameron told reporters as he arrived for an EU summit with six ex-Soviet states where he hopes to have initial contacts on his drive to reform the 28-nation bloc.

"But one thing throughout all of this will be constant and that is my determination to deliver for the British people a reform of the EU so they get a proper choice in that referendum," he said.