Ukraine war live updates: Ukraine pulls forces back in east as front line worsens; Kyiv desperately awaits U.S. weapon supplies

This is CNBC's live blog tracking developments on the war in Ukraine. See below for the latest updates. 

Ukrainian forces have been forced to retreat from several villages in eastern Ukraine as Russian forces advanced, the country's army chief said Sunday.

"The situation at the front [has] worsened," Ukraine's commander-in-chief, Col. Gen. Oleksandr Syrskyi, said on Telegram.

He said the "most difficult situation" was in the areas west of Russian-occupied Maryinka and Avdiivka, a town captured by Russian forces in February and that he had moved his forces "to new frontiers" west of the villages of Berdychi, Semenivka and Novomykhailivka in a bid to prevent casualties.

Russia had deployed four brigades in these areas as it launched offensives, Syrskyi said, and while it had achieved some tactical successes, it not yet achieved any "operational advantages."

Ukraine's President Volodymyr Zelenskyy pleaded on Sunday for the rapid delivery of U.S. military aid, saying supplies, pledged within the $61 billion aid package agreed in the U.S. last week, had not yet arrived.

"We are interacting with our partners at all levels to achieve the level of efficiency in assistance that is needed not only to hold our positions, but also to disrupt Russia's war plans," Zelenskyy said in his nightly address.

"We are still waiting for the supplies promised to Ukraine – we expect exactly the volume and content of supplies that can change the situation on the battlefield in the interests of Ukraine. And it is important that every agreement we have reached is implemented – everything that will yield practical results on the battlefield and boost the morale of everyone on the frontline," he said.

Zelenskyy said he had spoken to House Minority Leader