Trump's November election victory has cast doubt on the future of American aid for Ukraine, providing a limited window for billions of dollars in already authorized assistance to be provided before he is sworn in next month.

The package features drones, ammunition for precision HIMARS rocket launchers, and equipment and spare parts for artillery systems, tanks and armored vehicles, the Pentagon said in a statement.

The aid will be funded via the Ukraine Security Assistance Initiative, under which military equipment is procured from the defense industry or partners rather than drawn from American stocks, meaning it will not immediately arrive on the battlefield.

It follows a $725 million package announced on Monday that included a second tranche of landmines as well as anti-air and anti-armor weapons.

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 and claimed he could secure a ceasefire within hours -- takes over.

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.

- America 'weaker' alone -

US Defense Secretary Lloyd Austin on Saturday warned that failing to keep opposing Russia's actions would have dire consequences.

"We can continue to stand up to the Kremlin. Or we can let (Russian President Vladimir) Putin have his way -- and condemn our children and grandchildren to live in a world of chaos and conflict," Austin told the Reagan National Defense Forum in California.

"This administration has made its choice. And so has a bipartisan coalition in Congress. The next administration must make its own choice."

The defense chief also emphasized the importance of US allies and partners in his remarks -- a contrast to Trump's go-it-alone "America first" world view.

"Here is the stark military fact: our allies and partners are huge force multipliers," Austin said.

"Ultimately, America is weaker when it stands alone. And America is smaller when it stands apart," he said. "There is no such thing as a safe retreat from today's interwoven world."

The United States has spearheaded the push for international support for Ukraine, quickly forging a coalition to back Kyiv after Russia launched its full-scale invasion in 2022 and coordinating aid from dozens of countries.

Ukraine's international supporters have since then provided tens of billions of dollars in weapons, ammunition, training and other security aid that has been key to helping Kyiv resist Russian forces.