EU officials expressed shock at the "assault on US democracy" witnessed by the storming of the US Congress on Wednesday by thousands of supporters of outgoing President Donald Trump.
"To witness tonight's scenes in Washington DC is a shock," European Council president Charles Michel tweeted.
The president of the European Commission, Ursula von der Leyen, said: "I believe in the strength of US institutions and democracy. Peaceful transition of power is at the core.
"Joe Biden won the election. I look forward to working with him as the next President of the USA," she tweeted.
In a separate tweet, EU foreign policy chief Josep Borrell said: "In the eyes of the world, American democracy tonight appears under siege.
"This is an unseen assault on US democracy, its institutions and the rule of law. This is not America. The election results of 3 November must be fully respected," Borrell said.
He commended Biden, who had earlier given an address branding the protesters' forced entry into the Congress building an "insurrection".
"The strength of US democracy will prevail over extremist individuals," Borrell said.
Michel said in his tweet that the US Congress was "a temple of democracy" and added: "We trust the US to ensure a peaceful transfer of power to Joe Biden."