According to Ukraine's President Volodymyr Zelensky, the situation in the eastern frontline city of Bakhmut is getting "more and more difficult.".
For more than six months, Russian forces have been attempting to take the city.
Mr. Zelensky said, "The enemy is constantly destroying everything that can be used to defend our positions.".
The Ukrainian president made her comments as US Treasury Secretary Janet Yellen, who was in Kyiv on Monday, warned China against arming Russia.
A portion of the Donetsk region of Ukraine, which is under the control of Russia and its separatist allies, has seen some of the fiercest fighting since Russia invaded the country just over a year ago.
Russian troops have recently stepped up their attempts to take the industrial city, and they are making progress.
"Practically all roads" into the city were "under [Russian] fire control," according to Denis Pushilin, the separatist leader of the self-declared Donetsk People's Republic.
President Zelensky discussed the situation in his nightly address, noting that securing a foothold in Bakhmut and ensuring its defense were being severely jeopardized by Russia's renewed assault.
He expressed his gratitude to "each and every person holding the area heroically.".
Additionally, President Zelensky reiterated the need for the dispatch of contemporary combat aircraft in order to defend "the entire territory of our country" from "Russian terror.".
Janet Yellen revealed the most recent transfer of $1.25 billion (£1 billion) in economic and budget aid to Ukraine during her unexpected trip to Kyiv on Monday.
During her visit to Kyiv last week, Ms. Yellen reaffirmed US President Joe Biden's statement that Washington would support Ukraine for as long as it took to win the war.
Speaking to CNN, Ms. Yellen added that although the severe sanctions put in place against Russia by Western nations had not yet caused its economy to collapse, she anticipated that it would do so in the future.
She added that any attempt by China to supply such weapons to Russia would have "severe" repercussions. She also said that Russia's ability to replace military equipment lost in attacks on Ukraine was "gradually jeopardized.".
"We have been very clear that we will not tolerate systematic violations of the sanctions that we have imposed that are intended to deny Russia access to military hardware to carry out this war," she said.
And we have made it very clear to the Chinese government, as well as to Chinese businesses and financial institutions, that breaking these sanctions would have serious repercussions. ".
US Secretary of State Antony Blinken stated last week that China was thinking about giving Russia weapons and ammunition. Beijing vehemently refuted the assertion.
Many believed that last week's meeting in Moscow between China's top diplomat, Wang Yi, and Russian President Vladimir Putin was a sign of China's close ties to Russia.
