"Strong security guarantees, if provided by European countries, need a backup by the United States, not with boots on the ground, but we still need generally a backup from the US to make sure that the deterrence is there," Rutte said on a visit to Slovakia.

Kyiv's European backers are scrambling to come up with a plan after US President Donald Trump undercut Washington's allies by launching efforts with Moscow to end the war.

Britain has said it could deploy troops to Ukraine if needed to ensure any peace is lasting -- but insists the US would need to provide a "backstop".

UK media reported that Britain and France were working on a proposal to send a 30,000-strong "reassurance force" to Ukraine, if Washington committed to providing air cover based in a neighbouring country.

Rutte did not give any details on the plans being drawn up but he said that the United States has "certain capabilities... necessary to make it possible for European countries to help."

Ukraine insists that it needs guarantees under any deal that would ensure Russia would not be able to rearm and attack again.

"It is vital that any deal reached brings an enduring peace that Russia will never again try to take one more square kilometre of Ukrainian land," Rutte said.

"While there is much that still needs to be decided, there is no question that Europe has a vital role to play in securing peace in Ukraine."

Trump's administration has made clear that it has no intention of sending troops to Ukraine under any peace deal.

Instead it has said that Europe must do the heavy lifting to make sure any agreement Washington brokers is implemented.

At the same time Trump has rocked Europe by lashing out at Ukraine's leader Volodymyr Zelensky and sowed doubts over the US commitment to NATO.