"I'm proud that the United States will announce its latest security assistance package for Ukraine, valued at $200 million," Austin said alongside President Volodymyr Zelensky at the opening of a meeting of Kyiv's international supporters in Brussels.

The package includes air defence munitions, artillery and rocket ammunition and anti-tank weapons, among other items, the US defence chief said.

It is the first package announced since Congress dropped new funding for Kyiv from a recent bill to avert a US government shutdown -- a move that called into doubt Washington's continued commitment to aiding Ukraine's fight against invading Russian forces.

Austin nonetheless insisted Wednesday -- as he has before -- that the United States "will stand with Ukraine for as long as it takes."

Even in the absence of further action by Congress, the US government still has authority to withdraw more than $5 billion in equipment for Ukraine from American military stocks.

However, there is only $1.6 billion in remaining funding to replace donated gear, and it is unclear if Washington will provide assistance to Ukraine that creates gaps it cannot immediately fill.

Washington is by far the biggest donor of military aid to Kyiv.

Austin said the United States has committed some $43.9 billion in security assistance since Moscow launched its full-scale invasion of Ukraine in February 2022, while all other donors have promised more than $33 billion.

"I continue to firmly believe that our support for the forces of freedom in Ukraine will hold fast in any season or any storm," he said.