US President Joe Biden's administration is working against the clock to provide billions of dollars in aid to Kyiv before President-elect Donald Trump takes office, after which future assistance for Ukraine will be in doubt.

Less than two months before Trump is set to be sworn in, Secretary of State Antony Blinken said in a statement that the package was part of efforts "to ensure Ukraine has the capabilities it needs to defend itself against Russian aggression."

It includes anti-personnel landmines, ammunition for HIMARS precision rocket launchers, Stinger missiles, counter-drone systems, anti-armor weapons and artillery ammunition, Blinken said in a statement.

The United States announced a first shipment of landmines to Ukraine last month -- a major policy shift slammed by rights groups.

US Defense Secretary Lloyd Austin has said that the decision was necessitated by Russian forces leading with dismounted infantry units instead of vehicles.

The Ukrainians "have a need for things that can help slow down that effort on the part of the Russians," Austin told journalists last month.

The outgoing US administration is working to get as much aid as possible to Ukraine before Trump -- who has repeatedly criticized US assistance for Kyiv, claiming he could secure a ceasefire within hours -- takes over the presidency.

- 'Spend every dollar' -

Trump's comments have triggered fears in Kyiv and Europe about the future of US aid, and Ukraine's ability to withstand Russian attacks in the absence of further American support.

On Sunday, Ukrainian President Volodymyr Zelensky said that his country needed security guarantees from NATO and more weapons to defend itself before any talks with Russia.

Pentagon spokesman Major General Pat Ryder said Monday that all remaining US funding for Kyiv would be used.

"At the president's direction, we will spend every dollar that Congress has appropriated for Ukraine and to replenish our stockpiles," Ryder told journalists.

Speaking prior to the announcement of the latest package, he put the total aid that can still be drawn from US stockpiles at $6.8 billion, while more than $2.2 billion is available to procure weapons and equipment from the defense industry.

Austin spoke on Monday with his Ukrainian counterpart Rustem Umerov, providing "an update on the continued surge of US security assistance to Ukraine to provide the capabilities it needs to defend against Russian aggression," the Pentagon said.

The United States has been a key military backer of Ukraine, committing more than $60 billion in weapons, ammunition and other security aid since Russia launched its full-scale invasion in February 2022.