EU leaders are preparing to stage a special summit in November to tackle the deeply divisive question of the size of the European Union budget over the rest of the decade, Brussels sources told AFP.

A diplomatic source indicated that a meeting of the 27-member EU heads of state and government could be called in November, in the gap between scheduled October and December summits.

But an EU official added: "There is a question about when it is announced."

When pressed, the official added: "Of course, there are intensive negotiations at the minute, but it's clear that the EU budget in these years of austerity is going to be a huge issue."

An official from an EU member country also said "there is a 90 percent likelihood that an extraordinary summit will be organised in November on the financial perspectives," referring to the seven-year budgetary cycle covering the years 2014 to 2020.

None of the sources were able to put a precise date on a gathering.

The European Union's budget has long been an annual headache for the tens of thousands of mostly Brussels-based staff that run the supra-national organisation.

But arguments against ever-rising spending have sharpened since the financial and debt crises first bit in 2008.

United Kingdom Prime Minister David Cameron has led successive calls first for cuts and then a freeze on EU spending in real terms, and can be expected to be a vocal figure come the talks.

Leaders are due to meet already on October 18-19, when bailouts for Greece and Spain are expected to dominate the discussion, and again on December 13-14.