U.S. Defense Secretary Lloyd Austin said on Friday that Ukrainian forces were having some success in their operations in Kharkiv and Kherson.
Ukrainian troops have recaptured more than 700 square km (270 square miles) of territory in the south and in the eastern Kharkiv region, where they advanced up to 50 km (31 miles) into Russian lines and retaken more than 20 villages, a Ukrainian general said on Thursday.
"We see success in Kherson now, we see some success in Kharkiv and so that is very, very encouraging," Austin said during a news conference with his Czech counterpart in Prague.
The gains would be a serious blow for Russia, which Western intelligence services say has suffered huge casualties. They would also represent a big boost for Kyiv, which is keen to show its Western backers that it can change the facts on the ground by force and deserves continued support.
Some of the biggest gains appear to have been made this week during a surprise Ukrainian counteroffensive in the Kharkiv region of northeastern Ukraine, which saw Kyiv's forces make a sudden and deep thrust behind Russian lines.
On Thursday, Austin said that President Joe Biden had approved an additional $675 million in weapons to Ukraine as he and other defence ministers met in Germany to discuss how to continue supporting Ukraine in the long-term.
The latest announcements of military aid bring the total U.S. security assistance to Ukraine to $15.2 billion since Biden took office in January 2021.
The Kharkiv region borders Russia, and its main city Kharkiv has for months been struck by Russian missiles after Moscow failed to take it in the early stages of its Feb. 24 invasion.
Ukraine has for weeks been talking about a big counteroffensive in the south, which is also underway though details about it are sparse. Western military analysts believe Russia may have left itself exposed in other areas as it rushed to reinforce the south.
There is pressure on Kyiv to demonstrate progress on the ground before winter sets in, amid threats by Russian President Vladimir Putin to halt all energy shipments to Europe if Brussels goes ahead with a proposal to cap the price of Russian gas.
Russia has confirmed fighting in the Kharkiv region area but has not confirmed any territorial losses.
(Reporting by Idrees Ali, additonal reporting by Jan Lopatka; editing by John Stonestreet and Kim Coghill)
