“I think that it is necessary to have a peace mission — NATO, possibly some wider international structure — but a mission that will be able to defend itself, which will operate on Ukrainian territory,” Mr Kaczynski said at a news conference in Kyiv.

So far, NATO has maintained that it will not send troops to Ukraine in fear that it may escalate tensions and be interpreted as an act of war against Russia.

“I can’t preview what decisions will be made at this NATO conference and how NATO will respond to the Polish proposal. What I can say is American troops will not be on the ground in Ukraine at this moment,” the US ambassador to the United Nations, Linda Thomas-Greenfield, told CNN on Sunday.

During a news conference on Thursday, Piotr Müller, a Polish government spokesman, made it clear that Poland is not advocating “getting into direct conflict with Russia.” The proposed peacekeeping mission would only be stationed in the parts of Ukraine which are not occupied by Russia, “to send a clear signal that war crimes will not be accepted” Mr Müller explained.

Jens Stoltenberg, NATO’s secretary general, said during a news conference on Wednesday that while the alliance “supports peace efforts” and “calls on Russia and President Putin to withdraw its forces,” it has “no plans of deploying NATO troops on the ground in Ukraine.”

NATO has deployed peacekeeping missions to conflict-stricken countries in the past, such as Kosovo and Bosnia and Herzegovina, where the role of the troops was to ensure public safety and support international humanitarian efforts. However, these missions were usually launched after the end of military conflicts, and not while they were still in place.