The shift in US President Donald Trump's stance on Ukraine is becoming increasingly evident, giving the Ukrainian side hope for a tougher approach from the White House leader towards Russia to push it into negotiations.

Ukraine's leader will meet Trump in Washington a day after the US president agreed to face-to-face talks with his Russian counterpart.

Ukrainian President Volodymyr Zelensky is expected to push Trump for additional long-range weapons capable of striking targets inside Russian territory when he meets with Trump in Washington at the White House on Friday.

Despite warm rhetoric and promises of a summit, Moscow's tactic of buying time risks undermining real progress on the war.

"The U.S. Secret Service currently lacks a mechanism to reimburse local governments for their support," an agency spokesperson said.