Ukraine’s military says several attacks in the eastern Donetsk region have been repelled over the past 24 hours.
Russian forces claim they are about to capture the eastern city of Bakhmut, which has been at the center of months of heavy fighting.
The head of Russia’s Wagner private army claims he is “virtually surrounded” with limited access.
The US has announced a further $400m (£333m) in military aid to boost Kyiv’s depleted munitions stockpile.
The commander of Ukraine’s ground forces, Col. Gen. Oleksandr Serskyi, visited Bakhmut on Friday to hold meetings with local commanders on how to bolster frontline forces.
Russian troops have been trying to capture the city for six months.
Ukrainian President Volodymyr Zelensky warned this week that the situation on the eastern frontline was becoming “more and more difficult”.
A major concern for Ukraine is the continued depletion of its munitions stockpile as the increasingly intense war with Russia shows no signs of abating.
US Secretary of State Anthony Blanken said the country’s latest package included highly accurate Hummarus artillery rockets and howitzers “which Ukraine is using very effectively”.
President Zelensky had previously stressed that artillery and shells were needed to “stop Russia”.
The US is also sending strategic bridges ahead of an expected invasion of Ukraine.
The delivery of equipment that allows armored vehicles to cross rivers and ditches comes as several Ukrainian military officials and experts suggest the operation could begin in the coming weeks.
Also, a partial evacuation was ordered Thursday in the northeastern city of Kupiansk, Kharkiv region, which was liberated from Russian occupation last September.
Regional officials said children and families “with limited mobility” should leave because of “continuous” shelling by Russian forces.
In a statement on Friday, Mr Blanken said: “This military aid package includes more ammunition for the US-supplied Hammers and howitzers, which Ukraine is using so effectively to defend itself”.
He added that Washington would also send “Bradley infantry fighting vehicles, armored vehicle-launched bridges, demolition munitions and equipment, and other munitions for maintenance, training and support.”
Late last year, the Hymaras proved extremely useful during Ukraine’s lightning counteroffensive, which brought almost the entire Kharkiv region back under Kyiv’s control.
Those developments – and the liberation of the southern city of Kherson – were the most significant front-line changes since Russia’s withdrawal from areas around Kyiv in April.
In his statement, America’s top diplomat stressed that “the United States is also rallying the world to support Ukraine in defense of its sovereignty and territorial integrity”.
The announcement of the new U.S. military aid package comes amid reports in the U.S. media that Ukraine may now be dangerously low on artillery stockpiles, more than a year since Russia launched its full-scale offensive. has started
Both Ukraine and Russia are believed to be firing tens of thousands of artillery shells daily in what is seen as the height of the war in recent months.
The Ukrainian military has not publicly commented on the ammunition shortage.
However, President Zielinski said on Thursday that “artillery is the number one thing we need”.
He added that Kyiv also needs “massive amounts of shells” and warplanes to “remove” Russian troops from Ukrainian territory.
US President Joe Biden was expected to dominate the agenda for military aid to Ukraine during a meeting with German Chancellor Olaf Schulz in Washington on Friday.
Mr Biden thanked the German leader for his country’s “deep” support for Ukraine.
Mr Schulz said it was important to stress that this would continue “as long as it takes and as long as necessary”.
A number of Ukraine’s Western allies have pledged to provide tanks and artillery – but Kyiv says this must be done quickly to deter further Russian aggression.
