U.S. Secretary of State Antony Blinken arrived in Kyiv in a gesture of support as Ukraine's counteroffensive against Russian forces grinds into its fourth month with only small gains.

During his two-day visit, Blinken is likely to announce a new package of U.S. assistance worth more than $1 billion, a senior State Department official told reporters on the trip.

Blinken, on the first trip to Kyiv by a top U.S. official since the Ukrainian counteroffensive began, is expected to meet President Volodymyr Zelenskiy and Foreign Minister Dmytro Kuleba among other senior officials as well as civil society figures, the official said.

Several hours before his 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 U.S. officials as saying the Ukrainian counteroffensive has been too slow and hindered by poor tactics - criticism that angered Ukrainian officials and prompted 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.

U.S. officials have been careful not to publicly criticize 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, assess the battlefield needs as well as any steps that might be required to shore up Ukraine's energy security before roe ahead of the winter months.

"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."

RISING OPPOSITION TO UKRAINE AID

Blinken's visit follows the dismissal this week of Oleksii Reznikov who, as Ukraine's defence minister, had lobbied Washington and its allies for arms to fight the Russian invaders. Parliament was expected to confirm former lawmaker Rustem Umerov as his successor.

Despite staunch U.S. support for Ukraine so far since Russia's invasion in February last year, several Republican presidential hopefuls have questioned that aid, fuelling concerns over whether Washington will be able to back Ukraine at the same level once the U.S. 2024 election campaign intensifies.

The U.S. 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 U.S.-made F-16 fighter jets pledged by a number of NATO allies.

U.S. 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.