Poland, backed by aircraft from its NATO allies, shot down drones that had violated its airspace on Wednesday, the first time a member of the Western military alliance is known to have fired during Russia's war in Ukraine.
European leaders strongly condemned the drone incursions and demanded new sanctions against Moscow.
The United Nations Security Council was set to meet on Friday at Poland's request to discuss the incident.
Russia said its forces had been attacking Ukraine at the time of the incursions and that it had not intended to hit any targets in Poland. Trump told reporters in Washington on Thursday: "It could have been a mistake."
Polish Prime Minister Donald Tusk responded on X: "We would also wish that the drone attack on Poland was a mistake. But it wasn't. And we know it."
Poland is among the closest US allies in Europe, praised by the Trump administration for devoting the largest share of its economy to defence of any NATO ally, including the United States itself.
For its leader so directly to contradict Trump in public is almost unheard of, and a sign of Europe's alarm at the US president's willingness to give weight to Moscow's account.
Polish Deputy Defence Minister Cezary Tomczyk said: "I think this is a message that should reach President Trump today: there's no question of a mistake - this was a deliberate Russian attack."
Warsaw has portrayed the drone incursions as an attempt by Russia to test the capabilities of Poland and NATO to respond.
Polish Foreign Minister Radoslaw Sikorski was visiting Kyiv on Friday.
European leaders say it is the latest demonstration that Moscow has no interest in a peace deal in Ukraine, weeks after Trump hosted President Vladimir Putin in Alaska and withdrew a demand that Russia accept an immediate ceasefire.
France's outgoing foreign minister said the Russian ambassador would be summoned on Friday and Britain announced a new package of Russia-related sanctions.
Trump has repeatedly set deadlines for Moscow to agree a ceasefire or face new sanctions, only to row back.
European officials have been in Washington this week hoping to coordinate sanctions on Russia with the US administration.
Announcing such sanctions in tandem was previously standard practice but not taken place since Trump returned to office.
France said on Thursday it would deploy three Rafale fighter jets to help Poland protect its airspace and Germany said it would strengthen its commitment to NATO's eastern border.
Japan said it had decided to lower its price cap on Russian crude oil to punish Moscow for its continued war in Ukraine.
Russia and its close ally Belarus began a long-planned joint military exercise on Friday that will involve drills in both countries and in the Baltic and Barents seas.
Russia also pressed on with attacks on Ukraine, killing three people in the northern Ukrainian region of Sumy, local Ukrainian prosecutors said.
Ukrainian drones attacked Russia's northwestern port of Primorsk, setting fire to a vessel and a pumping station, the regional governor said. It was the first reported drone strike on one of the country's largest oil and fuel export terminals.
8°C