The head of Ukraine's presidential office has expressed confidence that the country will receive more military assistance from the United States and other allies to continue its offensives against Russian forces.

Andriy Yermak gave an exclusive interview to NHK in Ukraine's capital Kyiv on Saturday.

Yermak said the most important challenge is the situation in Donbas, especially Bakhmut. Donbas comprises the eastern regions of Donetsk and Luhansk.

The official said Ukrainian forces are taking up their positions, and are moving forward little by little in the fight for Bakhmut.

Yermak said Ukrainian forces in Bakhmut have to replicate the success of their comrades in the southern region of Kherson and the eastern region of Kharkiv. He said Ukraine's formula for success is not to stop in winter, or for the holidays.

Yermak accompanied Ukrainian President Volodymyr Zelenskyy on his visit to the United States last month.

Yermak said the Ukrainian delegation returned home with official confirmation that Kyiv will receive from the US and other allies everything it needs to win. He said the US and other partners have more confidence in Ukraine's victory.

US President Joe Biden pledged to provide Ukraine with more military aid, including the Patriot air defense system, when he hosted Zelenskyy at the White House on December 21.

Biden also disclosed on Wednesday that his administration was considering supplying Ukraine with armored fighting vehicles.