The idea was part of a security agreement that Poland and Ukraine signed last week, which allows for the interception of missiles and drones in Ukrainian airspace fired toward Poland.

Polish prime minister Donald Tusk had stressed that such a policy would only be implemented if it had complete support within NATO.

However, in an interview with Ukrainian broadcaster Edyni Novyni on Sunday, Stoltenberg expressed his opposition stating that while the alliance supported Ukraine in destroying Russian aircraft, it would not be directly involved.

Stoltenberg said: “NATO will support Ukraine, and we have recently increased our support... But NATO’s policy remains unchanged – we will not participate in this conflict.”

At the same time, he affirmed Ukraine’s right to self-defense, including striking inside Russian territory.

“Ukraine has the right to attack military targets on the territory of the aggressor country, Russia. This is clearly defined by international law, because this is a war that Russia started against Ukraine,” said the outgoing general-secretary of NATO.

Stoltenberg also welcomed the U.S. decision to allow Kyiv to use American missiles for attacks on Russian territory near the Ukrainian border in the Kharkiv region.

He stressed that different NATO countries had imposed different restrictions on the use of the weapons transferred to Ukraine, adding that while some had not set any restrictions at all, others had.

“Now, some allies are loosening their restrictions, particularly due to the warfare that Russia is attempting or already conducting in the Kharkiv region,” Stoltenberg said.