With the origin and ownership of the missile that hit Poland on Tuesday, killing two people, still uncertain, the United States and NATO countries said they would fully investigate before acting.
President Biden made that statement in Indonesia after meeting other Western leaders on the sidelines of a summit of the G20 big economies.
Biden said: "There is preliminary information that contests that [the missile was fired from Russian territory]. I don't want to say that until we completely investigate it, but it is unlikely in the lines of the trajectory that it was fired from Russia, but we’ll see."
NATO Secretary General Jens Stoltenberg said Wednesday the missile was probably the result of Ukrainian anti-aircraft fire but that Russia bears "ultimate responsibility" for the war.
"An investigation into this incident is ongoing, and we need to await its outcome.... But we have no indication that this was the result of a deliberate attack," Stoltenberg said after chairing a meeting of NATO ambassadors.
"Our preliminary analysis suggests that the incident was likely caused by a Ukrainian air defense missile fired to defend Ukrainian territory against Russian cruise missile attacks.
"But let me be clear, this is not Ukraine's fault," he continued.
"Russia bears ultimate responsibility as it continues its illegal war against Ukraine."
The Polish Foreign Ministry said the rocket fell on Przewodow, a village about six kilometers from the Ukrainian border, where it killed two people Tuesday.
Polish President Andrzej Duda told reporters it was "most likely a Russian-made missile", but that there was no concrete evidence of who fired it. Both Russia's long-range missiles and air defense missiles used by Ukraine use Russian designs.
Kyiv on Wednesday requested access to the site after Western officials said the explosion there was likely caused by Ukrainian air defenses.
"Ukraine requests immediate access to the site of the explosion," the secretary of Ukraine's national security and defense council, Oleksiy Danilov, said on Twitter, adding they were ready to hand over "evidence" regarding allegations against Russia.
Russian spokesman Dmitry Peskov told reporters that Russia had nothing to do with the incident, which he said had been caused by an S-300 air defense system.
"Photographs of the wreckage... were unequivocally identified by Russian military experts as fragments of a guided anti-aircraft missile of a Ukrainian S-300 air defense system," the Russian defense ministry said in a statement.
It added that "strikes were carried out on targets only on the territory of Ukraine and at a distance of no closer than 35 kilometers from the Ukrainian-Polish border."
But Ukrainian Foreign Minister Dmytro Kuleba earlier rejected as a "conspiracy theory" the idea that it may have been a Ukrainian missile.
However. Poland's President Andrzej Duda on Wednesday said it was "very likely" that the deadly missile that struck a Polish border village was from Ukraine's air defense.
"Absolutely nothing indicates that this was an intentional attack on Poland... It's very likely that it was a rocket used in anti-missile defense, meaning that it was used by Ukraine's defense forces," he told reporters.
Some Western leaders said that whoever fired the missile, Russia was ultimately responsible.
"They stressed that, whatever the outcome of that investigation, Putin's invasion of Ukraine is squarely to blame for the ongoing violence," British Prime Minister Rishi Sunak's office said after a meeting between Sunak and Canadian Prime Minister Justin Trudeau.
This report was compiled using data from Reuters and Agence France-Presse.