London, Muharram 27, 1437, Nov 9, 2015, SPA -- British Prime Minister David Cameron on Monday urged European Union leaders to be "flexible enough" to agree to a package of reforms, one day before he publishes a letter listing his demands ahead of an in-out referendum on Britain's membership, dpa reported. Cameron said he will set out his plans for "big and important changes" on Tuesday in his letter to EU President Donald Tusk, and hopes leaders of the other 27 EU nations will support his calls for reform. He has promised to renegotiate the terms of Britain's EU membership before holding an in-out referendum by the end of 2017, but he warned on Monday that he could campaign for Britain to leave the EU if he is not satisfied with the outcome of his negotiations. -- SPA 21:44 LOCAL TIME 18:44 GMT www.spa.gov.sa/w