Polish Prime Minister Mateusz Morawiecki said on Friday that Warsaw would make a formal submission to send a peacekeeping mission to Ukraine at the next NATO summit, Reuters reported.

Morawiecki had visited Kyiv on Tuesday along with Poland’s ruling party leader Jaroslaw Kaczynski.

With them were Czech Prime Minister Petr Fiala and Slovenian Prime Minister Janez Jansa in the first high-level international delegation visit to the Ukrainian capital since the beginning of the war on February 24.

Kaczynski had announced the idea of an armed peacekeeping mission during the visit.

“I think that it is necessary to have a peace mission, NATO, possibly some wider international structure,” Kaczynski said according to news agency Ukrinform. “But a mission that will be able to defend itself, which will operate on Ukrainian territory.”

Kaczynski said that the presence of a peace-keeping force with Ukraine’s permission would not be a pretext for further hostilities.

However, the next day, NATO allies refused to back Warsaw’s call, with Dutch Defense Minister Kajsa Ollongren saying: “I’m afraid we’re still in too early stages to talk about that.”

Estonian Defense Minister Kalle Laanet said a peacekeeping mission was “one of the possibilities” but any deployment would need the backing of the United Nations Security Council where Russia holds a veto.

U.K. defense minister Ben Wallace said he would need to “look at the details first” before any decision on such a peacekeeping mission is made.

Ukraine is not a member of NATO but has repeatedly called for it to do more to counter Russian aggression.

The main part of its demands is to impose a no-fly zone, which the alliance has ruled out over fears that it would lead to a shooting war with Russia.

World leaders have also expressed fears that it could spark a wider conflict involving a nuclear-armed adversary.

However, NATO has said that it would continue to give arms to Kyiv. NATO allies have been sending weapons to help Ukrainian forces, especially portable anti-tank and anti-aircraft missile systems.

On Tuesday, the alliance’s Secretary-General Jens Stoltenberg said there were no plans to deploy NATO troops on the ground in Ukraine.

Ukrainian President Volodymyr Zelensky admitted on Tuesday that he had accepted his country would not join the alliance, one of the demands made by Russian President Vladimir Putin.

Newsweek has contacted NATO for comment.