The EU’s most senior sanctions envoy is holding talks in Washington with US officials after Donald Trump said he was ready to take further action against Russia over the war in Ukraine.

David O’Sullivan, the EU sanctions envoy, is meeting US counterparts on Monday, as Europe and the US look for tougher measures to weaken Vladimir Putin’s war machine after Russia launched its largest-ever air attack on Ukraine over the weekend.

Ahead of those meetings, the head of the European Council, António Costa, hailed transatlantic cooperation over sanctions against Russia and said it was clear that the US remained engaged in supporting Ukraine.

A European Commission spokesperson also confirmed that its president, Ursula von der Leyen, spoke to the US vice-president, JD Vance, over the phone on Friday, and “the only topic during the call was Ukraine”.

Asked by a reporter at the White House on Sunday if he was ready to move to “the second phase” of sanctions against Russia, Trump responded: “Yeah I am,”without elaborating.

Trump also said that “certain European leaders are coming over to our country on Monday or Tuesday individually” and that he would speak to the Russian president soon.

Trump has previously threatened tougher measures against Putin, but each time has allowed deadlines to pass without action.

Speaking in Helsinki on Monday, Costa said the EU and US were “coordinating our efforts to align our sanctions, to be more effective” and to increase pressure on Putin to join peace negotiations with the Ukrainian president, Volodymyr Zelenskyy.

The German chancellor, Friedrich Merz, condemned Russia’s attacks on Ukraine, “which show further escalation”, a German government spokesperson said on Monday. The spokesperson also said Germany would welcome the US joining Europe in pushing for more sanctions against Russia.

In a coordinated move, France and Germany have proposed further sanctions targeting Russia’s energy revenues, including listing non-sanctioned oil majors, such as privately owned Lukoil, as well as going after refineries in foreign countries that re-export Russian oil to the EU. The EU’s two key players also propose increasing pressure on Russia’s civilian economy, via measures targeting civil aviation and engineering. “Russia continues its stalling tactics and persists in refusing a ceasefire,” said a Franco-German paper that calls for increased pressure.