Donald Trump's special envoy Steve Witkoff and top diplomat Marco Rubio will hold talks with European counterparts in Paris later on Thursday to discuss efforts to end the war in Ukraine.
Ukraine's foreign minister and defence minister have arrived in the French capital to take part in the discussions.
The talks, hosted by French President Emmanuel Macron, form the highest level of transatlantic engagement about the war since February.
European diplomats have said they will urge the US to put more pressure on Russia to agree an unconditional ceasefire.
"We want the US to use a bit more stick," one official said.
Ongoing efforts to secure a ceasefire come days after a Russian missile attack killed at least 35 people and injured 117 in the Ukrainian city of Sumy.
Earlier this month, at least 18 people died in a strike on a residential area in Kryvyi Rih.
Overnight on Wednesday, Ukrainian authorities said a Russian drone attack on the city of Dnipro killed three people, including a young girl.
US Secretary of State Marco Rubio and Witkoff will join meetings at the Elysée Palace attended by Macron, the UK's national security advisor Jonathan Powell, as well as other European national security advisers.
There will also be a separate meeting of foreign ministers, which UK Foreign Secretary David Lammy is expected to attend.
The US State Department said the focus would be on how to end the fighting in Ukraine, and that Witkoff would report on his meeting with Russian President Vladimir Putin last week.
Ukrainian President Volodymyr Zelensky's chief of staff Andriy Yermak said "we are working on important issues for the security of Ukraine and the whole of Europe".
When asked about the talks, Kremlin spokesman Dmitry Peskov said European leaders were focussed on "continuing the war".
In May 2023, prior to returning to the White House, Trump said he would be able to settle the war between Russia and Ukraine "in 24 hours".
His administration has taken action to drastically improve relations with Moscow, while seeking to broker a ceasefire between Russia and Ukraine.
Zelensky previously warned Ukraine would not accept a peace deal if his country was not involved any such agreement.
Tensions between Trump and Zelensky have been high since a heated confrontation at the White House in February, where the US leader chided Ukraine's president for not starting peace talks with Russia earlier.