It comes after Germany's likely next chancellor, Friedrich Merz, this week vowed billions of euros in extra spending on defence and infrastructure.

Germany's EU ambassador surprised his European counterparts during a Brussels meeting when he suggested giving member states more room to spend, beyond a four-year exemption proposed this week, several diplomats said.

The proposal marks a significant shift for a country that has, in the past, maintained a hardline stance on budgets and sought to avoid any loosening of spending rules.

With US President Donald Trump's pivot away from backing Ukraine casting doubt on future support for Europe as well, the bloc is planning a radical ramping up of defence investments to better protect itself.

EU leaders are set to approve the four-year exemption to allow member states to surge defence spending during an extraordinary summit in Brussels on Thursday.

But the German ambassador suggested that Brussels should be "going further", given the current geopolitical situation, one EU diplomat said.

However the ambassador's call that was not welcomed by other states with a frugal approach to spending.

"The Dutch and Swedes asked not to change the text," the diplomat added.

EU members are bound by spending rules demanding they keep the public deficit below three percent of economic output and debt at a maximum 60 percent of GDP.

The subject of changing the rules outright could be discussed during Thursday's summit, at which leaders are expected to endorse a plan by EU chief Ursula von der Leyen to spur defence investments and support Ukraine against Russia.

EU powerhouse Germany is set to pour billions more into defence after Merz said Tuesday that his centre-right CDU/CSU and the centre-left Social Democrats would propose to exempt more of the spending from the country's constitutionally enshrined "debt brake".

Ramping up defence expenditure, as the bloc is advocating, could make it difficult for member states to stay within the debt and deficit limits.

After long and painful negotiations to agree on a reform of the EU's spending rules, the bloc struck a deal last year -- before Trump's election victory in November.