EU chief Ursula von der Leyen on Tuesday presented a five-part plan to mobilise some US$844 billion for Europe's defence, and help provide "immediate" military support for Ukraine after Washington suspended military aid.

The move came hours after US President Donald Trump announced the aid freeze, intensifying Washington's push for a peace deal with Russia and confirming its pivot away from its European allies and partners in backing Kyiv's war effort.

"A new era is upon us," the European Commission president said in a letter presenting the plan to EU leaders, two days before a summit aimed at cementing joint action on support for Ukraine and boosting Europe's defences.

"'Rearm Europe' could mobilise close to US$844 billion of defence expenditures for a safe and resilient Europe," von der Leyen told reporters as she outlined the plan, which includes a US$158 billion loan facility along with steps to free up large-scale defence investments.

It was not immediately clear how fast funds could be made available under the proposals, which need approval by member states, nor how quickly this could translate into battlefield support for Kyiv.

It proposes that the EU ease strict budget rules, which oblige states to keep public deficits below three percent of gross domestic product, to allow them to ramp up spending on defence.

Secondly, the plan calls for a new "instrument" to provide US$157 billion of loans to member states for defence investment.

"We are talking about pan-European capability domains - for example, air and missile defence, artillery systems, missiles and ammunition drones and anti-drone systems," said von der Leyen.

Thursday's Brussels summit, after weekend crisis talks also involving Britain and Nato, comes as Europe contemplates the prospect of the United States withdrawing longer-term support from Ukraine and more broadly from its European allies. (AFP)