EU defence commissioner Andrius Kubilius floated creating a "powerful, standing 'European military force' of 100,000 troops" as a possible option to better protect the continent.

"How will we replace the 100,000-strong American standing military force, which is the back-bone military force in Europe?" he asked in a speech in Sweden.

The suggestion comes as US President Donald Trump has heightened fears among NATO allies over Washington's reliability by insisting he wants to take over Greenland.

Worries over Trump's commitment to Europe have already spurred countries to step up efforts to bolster their militaries in the face of the threat posed by Russia.

Ideas about establishing a central European army have floated around for years but have largely failed to gain traction as nations are wary of relinquishing control over their militaries.

The US has pushed its European allies to increasingly take over responsibility for their own security, and raised the prospect it could shift forces from Europe to focus on China.

"In such times, we should not run away from the most pressing questions on our institutional defence readiness," said Kubilius, a former Lithuanian prime minister.

In his speech Kubilius also advocated for the creation of a "European Security Council" of key powers -- including potentially Britain -- that could help the continent take decisions over its own defence quicker.

"The European Security Council could be composed of key permanent members, along with several rotational members," he said.

"In total around 10-12 members, with the task to discuss the most important issues in defence."

He said the first focus of such a body should be trying to change the dynamics in the war in Ukraine to ensure that Kyiv does not end up losing.

"We need to have a clear answer - how is the EU going to change that scenario?," he said.

"This is the reason why we need to have a European Security Council now!"