The United States on Wednesday unveiled additional aid to Ukraine worth more than $1 billion, including supply of depleted-uranium ammunition, with its top diplomat assuring President Volodymyr Zelenskyy of Washington's continued support during a visit to Kyiv.

U.S. Secretary of State Antony Blinken announced the aid at a press conference following meetings with Zelenskyy and other officials the same day during his fourth visit to the conflict-torn country since the Russian invasion began in February last year.

"We are determined in the United States to continue to walk side by side with you," Blinken told Zelenskyy during an open part of their meeting, according to the U.S. State Department.

U.S. Secretary of State Antony Blinken (L) and Ukrainian Foreign Minister Dmytro Kuleba hold a press conference in Kyiv on Sept. 6, 2023. (Pool photo/AP/Kyodo)

Blinken also met with Foreign Minister Dmytro Kuleba and visited a graveyard for those who have died in the conflict against Russia.

Ammunition made with depleted uranium, which is extremely dense, offers greater penetration power than other anti-tank weapons, though there are concerns that particles of the material could affect human health and the environment.

The department also said Blinken met with Danish Prime Minister Mette Frederiksen on his way to Ukraine the same day and discussed issues such as Copenhagen's decision to provide its U.S.-produced F-16 fighter jets to Ukraine.

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