LONDON (AP) — Former Prime Minister John Major warned Wednesday that the United Kingdom may break up if the country votes to withdraw from the European Union in a planned referendum.

Major told BBC radio that a vote to leave the EU would mean a "high probability" that Scotland would have a referendum of its own and decide to leave the U.K. Scotland voted last year to remain part of the U.K. after a bruising referendum campaign. Its leaders want to remain in the EU.

"The United Kingdom would be fractured, that would be very damaging," he said Wednesday.

British Prime Minister David Cameron is seeking concessions from Europe's leaders at a summit this week ahead of a planned referendum on Britain's membership to be held by the end of 2017.

German Chancellor Angela Merkel said she is willing to talk with Britain about concessions that will help the country to vote to stay in the EU.

But the German leader told lawmakers Wednesday that the issues of freedom of movement and equal treatment of EU citizens are non-negotiable.

Merkel said "these principles are not up for discussion" but that Germany wants the U.K. to "remain an active partner in a strong European Union."