The decision to send or not to send Patriot air defense systems to Ukraine belongs to each individual government, NATO chief Jens Stoltenberg said on Friday, responding to a question about Poland’s proposal to send Germany’s Patriot units to Kyiv, Reuters reports.

Berlin offered Warsaw the Patriot system to help defend its airspace after a missile landed in Poland last week, killing two people, but Polish Defense Minister Mariusz Blaszczak later asked Germany to send defense units to Ukraine instead.

German Defense Minister Christine Lambrecht rejected the request on Thursday. She said the German Patriot units are intended for use on NATO territory, and any use outside of that would require prior discussion with NATO and allies.

NATO Secretary General Jens Stoltenberg, however, spoke of a decision that must be made by each country individually.

“Specific decisions regarding specific systems are national decisions,” the head of NATO told reporters in Brussels.

“Sometimes there are end-user agreements and other things, so they have to consult with other allies. But ultimately it’s (decisions) for governments to make,” he added.

What might happen if NATO sends the Patriot

Asked whether NATO risks becoming a party to the conflict by sending Patriot systems to Ukraine, Stoltenberg said the allies have already supplied Kiev with modern weapons without sending NATO personnel.

“As it was done, when there was a need for specialists to work with these systems, be it air defense systems or other advanced artillery systems, Ukrainians were trained in a NATO country,” he said.