"The Secretary General will meet with President Zelensky on Wednesday. A number of European leaders are in Brussels for the European Council meeting and some of them may join to discuss ongoing support for Ukraine, in particular air defence," a NATO official said Monday.

European officials said that leaders expected to attend included French President Emmanuel Macron, German Chancellor Olaf Scholz, Polish leader Donald Tusk and British Prime Minister Keir Starmer.

The meeting comes as Ukraine's European allies have begun discussing the possibility of stationing foreign troops in Ukraine in case of a ceasefire with Russia.

US President-elect Trump has vowed to push for a quick deal to halt the fighting when he assumes office in January.

That has sparked fears in Kyiv and Europe that Ukraine could be pushed to make big concessions to Moscow after nearly three years of battling the Kremlin's invasion.

For now, officials insist that discussions on any settlement remain premature -- and Rutte has urged them not to debate possible peace conditions in public as it risks playing into Russia's hands.

Moscow insists it is sticking to its goals in Ukraine and is currently making advances on the front line against Ukraine's fatigued forces.

"There has to be peace in order to send peacekeepers, and Russia does not want peace," EU foreign policy chief Kaja Kallas said Monday in Brussels.

"That is very clear."

Zelensky on Thursday is then set to attend a summit with the EU's 27 leaders.