(NEXSTAR) – Russia launched a wave of deadly airstrikes on Kyiv early Thursday, killing at least 18 people and injuring 48 others, in what Ukrainian officials say is the most intense assault on the capital in weeks. The escalation threatens to derail ongoing efforts by the Trump administration to broker a peace deal between Russia and Ukraine. White House Press Secretary Karoline Leavitt said President Donald Trump was “not happy” about the attacks but “not surprised.” Earlier this month, Trump held separate meetings with Russian President Vladimir Putin and Ukrainian President Volodymyr Zelenskyy. The former president expressed interest in a potential trilateral peace summit involving all three leaders. But following Thursday’s strikes, Leavitt acknowledged that progress may be stalling. “Perhaps both sides of this war are not ready to end it themselves,” she said. “The president wants it to end, but the leaders of these two countries need to want it to end as well.” European leaders are also expressing growing frustration. One EU government building was reportedly damaged in the latest barrage. “We cannot be naive,” NATO Secretary-General Mark Rutt said during a press briefing. “It’s clear Putin is trying to seize as much Ukrainian territory as possible before agreeing to any ceasefire.” Rutt added that negotiations are underway to finalize a security agreement for Ukraine and to organize a three-way summit between Trump, Putin, and Zelenskyy. The White House has not confirmed a date for the proposed meeting.