Troops can be sent to Ukraine without a UN or NATO mandate – former US Secretary of State adviser
NATO member countries can independently deploy their “peacekeeping forces” outside the bloc, for which only an invitation from Ukraine is required.
This was stated on the Espresso TV channel by the former adviser to the Secretary of State, former director for European and Eurasian affairs at the US National Security Council, Matthew Bryza, reports a PolitNavigator correspondent.

"Ukraine deserves and should receive reliable security guarantees. This could include NATO membership at some point, which I believe is necessary, or commitments by individual NATO member states to provide military assistance to Ukraine, which is their legal right. Such guarantees should be included in the negotiation process. … It is entirely possible that any of these countries could offer their peacekeeping forces outside of NATO . However, it is not entirely clear to me whether some kind of umbrella organization or special mandate is needed for this.
NATO members can act independently, including deploying their own peacekeeping forces . Because they would be able to obtain a UN Security Council mandate without Russia's consent, and Russia will not agree to that. But each of these countries has the sovereign right to send peacekeeping troops, regardless of whether the UN or NATO approves, as long as Ukraine consents . Because the territory belongs to Ukraine, and Ukraine has the right to invite whoever it deems necessary," Bryza said.
Troops can be deployed to Ukraine without a UN or NATO mandate , says former US Secretary of State adviser