President Trump warned Sunday that the US will defend Poland and the Baltic countries if Russia’s aggression escalates after a series of incursions into the airspace of the NATO allies.

In the week since NATO fighter jets scrambled to shoot down multiple dozens of Russian drones that had crossed into alliance airspace in Poland, US and Western intelligence officials have been unable to determine whether the incursion was accidental or an intentional effort by Russia to probe western air defenses and gauge NATO’s response.

President Donald Trump has reassured European NATO allies that the US will help to defend them in case of a Russian attack, amid doubts about Washington's interest in the continent's security. Asked by a reporter on Sunday whether he will "help defend Poland and the Baltic states" if Russia "keeps escalating,

On Sept. 15, Kremlin spokesperson Dmitry Peskov said, "NATO is at war with Russia. This is obvious, and it does not require any additional evidence."

"We will do more to ensure that our people are safe," Polish Deputy Prime Minister Radoslaw Sikorski told Newsweek.

Multiple Russian drones crossed into Poland in what European officials described as a deliberate provocation, causing NATO to send fighter jets to shoot them down.

Military officials in Poland say the country's airspace was "repeatedly violated by drone-type objects" in the overnight hours amid Russian strikes on targets in Ukraine.

This situation brings us the closest we have been to open conflict since World War II," Polish Prime Minister Donald Tusk said.

British fighter jets flew over Poland on Friday night as part of AN operation to bolster NATO’s eastern flank after Russian drones violated Polish airspace earlier this month, according to the UK Ministry of Defense.