US Secretary of State Antony Blinken arrived in Kyiv on an unannounced visit on Wednesday - in a gesture of support as Ukraine's counteroffensive against Russian forces grinds into its fourth month with marginal gains.
Mr Blinken is expected to announce a new package of US assistance worth more than $1 billion during his two-day visit, a senior State Department official told reporters on the trip.
During his visit, Mr Blinken is expected to meet President Volodymyr Zelensky and Foreign Minister Dmytro Kuleba among other senior officials as well as civil society figures, the official said.
It marks the first trip to Kyiv by a top US official since the Ukrainian counteroffensive began.
Several hours before Mr Blinken’s arrival, Russia carried out air strikes on Kyiv and the southern region of Odesa.
No casualties were reported in the capital but a civilian was killed and port infrastructure damaged in the south, Ukrainian officials said.
Media reports have cited unidentified US officials as saying the Ukrainian counteroffensive has been too slow and hindered by poor tactics - criticism that angered Ukrainian officials and prompted Mr Kuleba to tell critics to "shut up".
Ukraine has retaken more than a dozen villages and small settlements in its offensive but its soldiers' push into Russian-held territory has been slowed by minefields and miles of trenches.
US officials have been careful not to publicly criticise Ukraine's military tactics, and last week said they had seen notable Ukrainian progress in the previous 72 hours of its push in the southeast.
The State Department official, who spoke on condition of anonymity, said Washington would like to have a discussion with the Ukrainians on how the offensive is going, and assess the battlefield needs.
"I think what's most important is that we get a real assessment from the Ukrainians themselves," the official said. "We want to see, hear how they intend to push forward in the coming weeks."
The US government has so far provided more than $43 billion in weaponry and other military aid to Ukraine. A new package of security assistance is set to be announced this week, Reuters reported on Friday.
Kyiv is hoping to receive US-made F-16 fighter jets pledged by a number of NATO allies.
US President Joe Biden asked Congress in August to approve about $40 billion in additional spending, including $24 billion for Ukraine and other international needs.
The request could face opposition in Congress, where some far-right Republicans - especially those with close ties to former President Donald Trump - want to pare back the billions in assistance Washington has sent to Ukraine.