WASHINGTON: United States President Joe Biden announced US$2.5 billion in additional security assistance for Ukraine on Monday (Dec 30) as he uses his final weeks in office to surge military aid to Kyiv before President-elect Donald Trump takes power.

"At my direction, the US will continue to work relentlessly to strengthen Ukraine’s position in this war over the remainder of my time in office," Biden said in a statement.

Biden's announcement includes US$1.25 billion in military aid drawn from US stockpiles and a US$1.22 billion Ukraine Security Assistance Initiative (USAI) package, the final USAI package of Biden's time in office.

Under USAI, military equipment is procured from the defence industry or partners, rather than drawn from American stocks, meaning it can take months or years to arrive on the battlefield.

Russia's invasion of Ukraine is approaching the three-year mark and recently the Russians have used North Korean troops to bolster their fighting position.

North Korean forces are experiencing mass casualties on the front lines of Russia's war against Ukraine, with 1,000 of their troops killed or wounded in the last week alone in Russia's Kursk region, White House spokesperson John Kirby told reporters on Friday.

In a statement, Biden said the new assistance will provide Ukraine with "an immediate influx of capabilities that it continues to use to great effect on the battlefield and longer-term supplies of air defense, artillery, and other critical weapons systems".

Nearly three years into the war, Washington has committed US$175 billion in total aid for Ukraine, but it is uncertain if the aid will continue at that pace under Trump, who replaces Biden on Jan 20. Trump has said he wants to bring the war to a swift end.

During the presidential election campaign, Trump questioned the level of US involvement in the conflict, suggesting European allies should bear more of the financial burden.

Some of his fellow Republicans - who will control both the House of Representatives and Senate starting next month - have also cooled on sending more aid to Kyiv.

Biden said the Defense Department is in the process of delivering hundreds of thousands of artillery rounds, thousands of rockets, and hundreds of armored vehicles "which will strengthen Ukraine’s hand as it heads into the winter".