"You have to intrude into national politics when you have joint money, and that's what's really at stake," says German economist Guntram Wolff.
The biggest obstacle to a massive EU coronavirus recovery package is not money, but rather a tug-of-war over political sovereignty, according to a German economist.
On Monday morning, after more than three days of talks, European leaders still had not reached a deal on a joint rescue fund to tackle the economic impact of the coronavirus pandemic.
"This is really a very, very difficult negotiation because it is not only about this one new set of big money, but it really changes the contours of monetary union," Guntram Wolff, Director of the Bruegel economic think tank in Brussels, told Euronews.
"It’s the first time the EU borrows money to give it as grants to countries. So it's really a game-changer in terms of how this monetary union, how this European Union works."
The EU summit in Brussels was supposed to last only two days. But negotiations went on into the early hours of Monday morning and were due to pick up again in the afternoon.
The major sticking point remains the size and terms of a massive coronavirus recovery fund – with the so-called 'frugal' nations of Austria, Sweden, Denmark, the Netherlands, and now Finland insisting on tough conditions on how member states will get to spend their money.
Wolff says the real obstacle isn't money but political sovereignty.
"The more difficult issue is really what is called conditionality – or you can call it supervision, or you can call it control of the money," Wolff said.
"This is, in a sense, about how to share sovereignty, and that's why it's so difficult."
Dutch Prime Minister Mark Rutte wants a link to be made between the handout of EU funds and the rule of law – a connection aimed at Poland and Hungary, countries with right-wing populist governments that many in the EU think are sliding away from democratic rule.
"It's not so much about the five or 10 billion more or less that any country will give or pay. It's really about what does it mean in terms of intrusion into national politics, which I think is unavoidable," said Wolff.
"I mean, you have to intrude into national politics when you have joint money, and that's what's really at stake."
Watch excerpts from the interview in the video player above.