‘Given the trajectory of the rocket it was unlikely it was fired from Russia, he added, "but we'll see’
The attack, which killed two people at a village about 6 kilometres from the frontier with Ukraine late on Tuesday, comes as tensions are already high with Russia over its February invasion of Ukraine. On Tuesday, Moscow fired a missile barrage at Ukrainian infrastructure, causing energy outages across the country.
Asked if the rocket that reached Poland had been fired from Russia, Biden told reporters in Bali, where he is attending the Group of 20 summit, "there is preliminary information that contests that." Given the trajectory of the rocket it was unlikely it was fired from Russia, he added, "but we'll see."
The incident in Poland is an attempt to provoke a direct clash between Russia and NATO, the head of the permanent mission of Russia to the United Nations said on Wednesday.
"There is an attempt to provoke a direct military clash between NATO and Russia, with all the consequences for the world," Dmitry Polyansky said on his Telegram channel.
Turkish president Recep Tayyip Erdogan cautioned against allegations the missiles that fell in Poland had originated from Russia despite Moscow's denials, telling the Group of 20 summit that it was an act of "provocation."
Mr Erdogan said alleging the missiles that fell in Poland had originated in Russia despite Moscow's denial is an act of "provocation" that is not right and should be avoided.
"I respect the statement made by Russia," Erdogan said at G-20. "Russia's saying that 'we have nothing to do with this' is important for us."
He added that as soon as he gets back, he will get on the phone with Putin for a dialog.
The plea for caution was echoed by German Chancellor Olaf Scholz, who called for a thorough probe of what he called a "terrible incident," while a senior French official said nobody wanted an escalation with Russia that could spin out of control. Identifying that the missile was Russian-made did not prove who launched it, the official said.
The Associated Press cited unnamed US officials as saying initial findings pointed to the rocket being fired by Ukrainian forces at an incoming Russian projectile.
One official from a Group of Seven country said it was possible that Russia's military had missed an intended target from inside Ukraine, or that a Ukrainian countermeasure had knocked the rocket off course. There would be little incentive for Russia to deliberately strike Poland, the person said, given the risk of a response from the North Atlantic Treaty Organization.
Since Russia invaded Ukraine, NATO members have repeatedly aired concerns about being drawn directly into the conflict. While they have supported Ukraine with weapons and financial aid, Europe and the US have drawn the line at sending it the longest range missile systems and advanced fighter jets and refused to support Ukraine's calls to set up an air defence zone over its airspace.
Russia's Defence Ministry denied its forces had aimed missiles at targets near Ukraine's border with Poland. Polish President Andrzej Duda said it was unclear who had launched the rocket that struck the village.
Russia has launched missile attacks from occupied areas of Ukraine since it invaded in February. It has also fired them from its neighbouring ally Belarus, and from aircraft and ships in the Black Sea.
Poland has said it is still investigating what happened. In the meantime, Duda said he was highly likely to invoke what is known as Article 4 of the North Atlantic Treaty Organization charter, which would kick off a discussion within the military alliance ahead of any potential response. NATO ambassadors will hold an emergency meeting on Wednesday morning.
Ukrainian President Volodymyr Zelensky said on Tuesday that Russia had attacked with missiles that knocked out power for large parts of the population.
Russian President Vladimir Putin is increasingly turning to missile strikes as his troops struggle on the ground in a war in its ninth month. His military recently withdrew from a key city in southern Ukraine that was captured early in the war, the latest setback on the battlefield.
Two people at the scene of the explosion in Poland, who asked not to be named, said a farm building had suffered damage. One said that a blast had shaken the windows in their car some 2 kilometres away. The second said police and military personnel had sealed off the area and asked everyone to leave the farm but that homes nearby had not been evacuated.
It's not the first time since Russia invaded Ukraine that objects have entered NATO airspace. In March, a six-ton unmanned reconnaissance drone streaked across eastern Europe and crashed in the Croatian capital of Zagreb.
Biden spoke by phone with his Polish counterpart Andrzej Duda, offering full U.S. support for and assistance with Poland's investigation and reaffirming America's commitment to NATO, according to a White House statement. US Defence Secretary Lloyd Austin spoke with his Polish counterpart as well.
G-7 leaders met on Wednesday morning on the sidelines of the G-20, alongside those from the European Union and European Commission. In a statement issued afterward they condemned the latest Russian strikes on Ukraine and offered support for Poland in its investigation.
An official whose leader attended the meeting downplayed the idea the Poland blast would see things escalate toward any sort of military response. Asking not to be identified discussing private matters, the official said leaders were working on rallying behind Ukraine.
European Council President Charles Michel tweeted that he spoke with Prime Minister Mateusz Morawiecki and "assured him of full EU unity and solidarity in support of Poland." Morawiecki said Poland had put its military on heightened alert near the border and would boost troop numbers there.
Earlier on Tuesday, a barrage of missiles targeted Kyiv and other locations across Ukraine, hitting civilians and critical infrastructure in what authorities said was the broadest such assault since the Russian invasion. Ukraine's air-defence forces said around 100 missiles were launched, exceeding the number from Oct. 10, when a broad attack hit Ukrainian settlements across the country and leveled infrastructure.
The missiles landing in Ukraine knocked out power for some 7 million households across much of the country, Kyrylo Tymoshenko, the Ukrainian president's deputy chief of staff, said in televised comments.