The air raid sirens howl seconds before or after waves of missiles strike apartment buildings, power plants and warehouses. But this week, Ukraine's partners did not provide intelligence data from NATO's early-warning satellites, Zelenskyy said.
The constellation of military satellites detects Russian ballistic missile attacks by thermal flames seconds after launch, giving Ukrainians up to 10 minutes to sound sirens and send emergency text messages.
"That's what helps prevent the killings," Zelenskyy said.
Ukraine's ground radars can only detect incoming missiles at speeds of 6,000 to 12,000 km/h.
Trump denied that Washington has stopped sharing intelligence, but Ukrainian observers have a different explanation: the US president wants to pressure Kyiv into an energy ceasefire to drive down global oil prices before the midterm elections.
Lieutenant-General Ihor Romanenko, former deputy head of Ukraine's general staff, said: "Trump pressures our president, pressures Ukraine" to "get advantage by any means necessary in the election campaign." The lack of intelligence data "significantly affects the effectiveness of air defence" and reduces the precision of Ukrainian strikes deep inside Russia.
On Sunday, Trump announced on social media an "energy ceasefire," saying "effective immediately" both parties have agreed not to strike energy infrastructure. Kyiv said the announcement was a surprise, and Moscow has not confirmed its support. Russian strikes on energy sites have continued.