Biden says 'unlikely' missile that hit Poland was fired from Russia

President Joe Biden vowed to "find out exactly what happened" after speaking by phone with Polish President Andrzej Duda and NATO Secretary General Jens Stoltenberg about a deadly explosion near Poland’s border with Ukraine.

Asked by a reporter whether the missile was fired from Russia, Biden said there was “preliminary information that contests that.”

“I don’t want to say that until we completely investigate, but it is unlikely ... that it was fired from Russia,” Biden said.

Biden, who is in Indonesia for the annual Group of 20 summit of leading rich and developing countries, said leaders of NATO and the Group of Seven leading industrialized countries agreed to "support Poland’s investigation into the explosion" at an unscheduled roundtable meeting to discuss the situation in Europe.

He added that they would “collectively determine our next step as we investigate and proceed.”

It was not immediately clear what caused the blast, which followed an intense wave of Russian airstrikes on cities across Ukraine on Tuesday, forcing widespread blackouts and hitting residential buildings in the capital, Kyiv.

Biden said he updated leaders at the roundtable meeting — including French President Emmanuel Macron, German Chancellor Olaf Scholz, Canadian Prime Minister Justin Trudeau, Italian Prime Minister Giorgia Meloni, Japanese Prime Minister Kishida Fumio, British Prime Minister Rishi Sunak, European Commission President Ursula von der Leyen and European Council President Charles Michel — about his calls with Duda and Stoltenberg.

In a readout of his call with Duda, the White House said Biden “offered full U.S support for and assistance with Poland’s investigation” and “reaffirmed the United States’ ironclad commitment to NATO,” which Poland is a member of.

The two leaders also agreed to remain in “close touch to determine appropriate next steps as the investigation proceeds,” the White House said.

The Polish Foreign Affairs Ministry issued a statement after the explosion Tuesday saying “a Russian-made missile fell, killing two citizens of the Republic of Poland,” in the southeastern village of Przewodów. The statement did not specify who was responsible.

Biden’s calls with Duda and Stoltenberg took place before the Foreign Affairs Ministry’s statement. At a meeting on the sidelines of the G-20, Biden and Sunak also discussed the explosion their support for Poland's investigation.

The Polish government decided to increase its military readiness at an emergency security and defense meeting after the explosion.

Russia has pushed back against suggestions that the explosion was caused by Russian missiles landing inside Polish borders.

“The statements of the Polish media and officials about the alleged fall of ‘Russian’ missiles in the area of the settlement of Przewodów, is a deliberate provocation in order to escalate the situation,” the Russian Ministry of Defense said in a statement on Telegram, referring to the village widely reported to have been hit.

Russian President Vladimir Putin decided not to attend this year’s G-20 meeting, instead sending Foreign Minister Sergey Lavrov.

“Russia has chosen to escalate in Ukraine — while we are meeting,” Biden said in Bali, referring to Moscow’s renewed attacks on Western Ukraine. “We support Ukraine fully in this moment, and we have since the start of this conflict. And we are going to continue to do whatever it takes to give them the capacity to defend themselves.”

National Security Council spokesperson Adrienne Watson said Tuesday afternoon that the White House was aware of the reports out of Poland and that it was working with the Polish government “to gather more information.” She said that national security adviser Jake Sullivan had spoken with the chief of the National Security Bureau of Poland, Jacek Siewiera, but that she could not confirm any details of the event at that time.

Biden, who was briefed about the explosion as he woke up in Bali on Wednesday morning, is expected to leave Indonesia on Wednesday to travel back to Washington.

Following the isolationist foreign policy approach of his predecessor, Donald Trump, Biden has sought to position himself as a champion of U.S. alliances, including NATO.

Since Russia invaded Ukraine in February, Biden has repeatedly spoken about the strength of the NATO alliance and has said the “United States will defend every inch of NATO territory.”

This article was originally published on NBCNews.com