EU leaders clashed at a stormy summit to decide the bloc's seven-year budget after Brexit, with bitter divisions between penny-pinching rich nations, poorer ones wanting to preserve spending and others wanting to fund grand global ambitions.

The tussle for money is a Brussels ritual, but is especially problematic this time around because of Britain's departure from the EU. 

The "Brexit gap" caused by the loss of the UK's contribution is €75 billion over the 2021-2027 period, but French President Emmanuel Macron insisted this must not mean the EU should trim its ambitions by cutting spending.

German Chancellor Angela Merkel warned there were "major differences" to overcome among the 27 countries, as some officials braced for talks to drag into the weekend. 

Mrs Merkel said as she arrived: "We are not satisfied with the current situation because the balance within the net payers has not yet been properly negotiated." 

Summit host Charles Michel, the EU Council president, kicked off the day with one-on-one meetings with leaders of the 27 states starting with Sweden, one of the so-called "frugal four" opposed to big budget increases.

"I am convinced that it will be possible to make progress in the next hours or in the next days," Mr Michel told reporters.

Once gathered, an EU source said leaders "respectfully" shared their well-known views, making plain the deep divisions and the hard work needed to forge a deal.

Some EU sources suggested differences are so great the summit could end earlier than thought and the can kicked down the road to another summit -- or two -- in the coming months.

French President Emmanuel Macron

Mr Macron, who wants farm payments protected and more money for European defence projects, said he was ready for the long haul.

"I will take all the time that is needed to get an ambitious agreement that defends the interests I represent," he said, insisting that with "a spirit of compromise and ambition" a deal could be found.

Mr Macron added it would be "unacceptable for Europe to compensate for the British departure by reducing its means."

But Finnish Prime Minister Sanna Marin slapped down his call for post-Brexit largesse, saying the EU had to be "realistic" following the departure of one of its biggest net contributors.

The minimum spending in the multi-annual financial framework (MFF), as the long-term budget is called, is just over one trillion euros. 

The discord is over how much this budget should increase by, how spending might be shifted between priorities and how much each member state should pay as a percentage of its gross domestic product (GDP).

Another touchy issue is whether budget rebates pocketed by a few wealthier countries should still exist.

The last MFF came in at €1.08 trillion (in 2018 prices). 

The "frugal four", Austria, Denmark, the Netherlands and Sweden, want to rein in the budget and make up only some of the ground of the Brexit gap. 

They also want to keep their rebates, as does Germany.

Austrian Chancellor Sebastian Kurz struck a tough note on Twitter, insisting Vienna's budget contributions must not "grow immeasurably" and rejecting a compromise proposed by Mr Michel.

Dutch Prime Minister Mark Rutte tweeted a picture of himself and the other "frugals" insisting for lower spending, while adding that he had come to Brussels with some leisurely reading, confident that his position would not budge.

At the high end of spending demands is the European Parliament, which wants the MFF expanded to €1.32 trillion to pay for costly goals such as turning the European Union into a carbon-neutral economy within three decades.

A "friends of cohesion" group of mostly eastern and southern EU nations wants to ringfence money it gets to help bring infrastructure and society up to the level of wealthier counterparts.

Agriculturally sensitive countries such as France, Spain and Poland are also looking to preserve farmers' subsidies. 

The European Commission, which aims for a "geopolitical" mantle under President Ursula von der Leyen, is trying for a target of €1.13 trillion.

Ahead of the summit, Mr Michel proposed an MFF of €1.09 trillion, making cuts to cohesion funds and farm subsidies to finance other priority areas.

His plan, though, has little support.

The European Parliament has rejected it as too little. 

Germany says it is a "step backwards" and Spain has criticised it for "not recognising the role of agriculture" in EU cohesion.

"The proposal is unacceptable, it's a series of cuts," European Parliament President David Sassoli told reporters after making his case to leaders.