The decision whether to send Patriot air defence units to Ukraine lies with the specific nations, NATO's chief said on Friday when asked about Polish demands for Germany to pass on Patriot units to Kyiv.

Berlin offered Warsaw the Patriot system to help secure its airspace after a stray missile crashed and killed two people in Poland last week but Polish Defence Minister Mariusz Blaszczak later asked Germany to send the fire units to Ukraine instead.

On Thursday, German Defence Minister Christine Lambrecht countered this demand.

She said Germany's Patriot units were intended for use on NATO territory, and any use outside NATO territory would require prior discussions with NATO and the allies.

NATO Secretary-General Jens Stoltenberg, however, spoke of a national decision.

"The specific decisions on specific systems are national decisions," he told reporters in Brussels.

"Sometimes there are end users agreements and other things so they need to consult with other allies. But at the end of the day, it (the decision) has to be taken by the national governments," he added.

Patriot is produced by the U.S. company Raytheon (RTX.N).

Responding to a question whether NATO risked becoming a party to the conflict by sending Patriot units to Ukraine, Stoltenberg noted that allies already had delivered advanced weapons to Kyiv without sending NATO personnel along.

"The way this has been done is that when there is a need for specialists to operate these systems, be it air defence systems or other advanced artillery systems, the Ukrainians have received training in a NATO country," he said. (Reuters)