Ukraine's top negotiator Rustem Umerov has arrived in Miami for a series of meetings with US representatives as the Ukrainian military said it fired on a Russian warship in the Caspian Sea.
Umerov is tasked with discussing a possible prisoner-of-war swap and stepping up diplomatic efforts to end the war, President Volodymyr Zelenskiy said on X.
Ukraine hoped US envoys Steve Witkoff and Jared Kushner would travel to Ukraine earlier this year but the visit never happened.
The US focus has largely moved away from Ukraine amid the war in Iran.
The United States-brokered talks are deadlocked over Ukraine's eastern Donetsk region.
Russia demands Ukraine pull troops back from parts of the region it has failed to capture in its four-year full-scale invasion.
Ukraine says it will not cede land that it controls.
"We are in constant communication with the American side and know about the relevant contacts of our partners with the Russian side. We are working to ensure that this helps bring a dignified peace closer and guarantee security," Zelenskiy said.
He added that Umerov received "several specific security-related instructions" regarding bilateral co-operation with the US.
The last round of trilateral Ukraine-Russia talks involving US representatives took place in February.
Ukrainian and Russian representatives have only had separate talks with the US team since.
Ukraine's military said on Thursday it had fired on a Russian warship capable of launching Kalibr cruise missiles.
A Karakurt-class corvette was hit, Ukraine's General Staff said in a statement on Facebook.
The military released a thermal image it said showed the vessel after the strike, likely captured by the attacking drone.
The extent of the damage is unclear.
According to Ukrainian officials, the corvette was stationed in the city of Kaspiysk in the Russian republic of Dagestan in the North Caucasus.
US President Donald Trump and Russian leader Vladimir Putin held a call on April 29 discussing a potential ceasefire.
Russia's defence ministry said on Thursday it had declared a ceasefire from midnight on Friday until Sunday to mark the anniversary of the defeat of Nazi Germany in World War II.
"During the celebration of the 81st anniversary of the Soviet people's victory in the Great Patriotic War, from midnight on May 8 to May 10, the Russian side is declaring a ceasefire," the ministry said on Telegram.
Russian President Vladimir Putin had on Monday declared a two-day ceasefire would be observed.
with DPA