U.S. President Joe Biden marked Ukraine's Independence Day on Wednesday with $3 billion in security assistance, Washington's largest aid package since Russia's invasion six months ago.

The aid, announced on Kyiv's Independence Day, comes as U.S. officials warn that Russia appears to be planning to launch fresh attacks on Ukraine's civilian infrastructure and government facilities in coming days.

"The United States of America is committed to supporting the people of Ukraine as they continue the fight to defend their sovereignty," Biden said in a statement announcing the package, noting Kyiv's "bittersweet" anniversary of independence from Russian-dominated Soviet rule 31 years ago.

The approximately $2.98 billion in assistance "will allow Ukraine to acquire air defense systems, artillery systems and munitions, counter-unmanned aerial systems, and radars to ensure it can continue to defend itself over the long term," he said.

In total, the United States has committed approximately $10.6 billion in security assistance to Ukraine since the beginning of the Biden administration in January 2021. Since 2014, the United States has committed more than $12.6 billion in security assistance to Ukraine.

The new package uses funds from the Ukraine Security Assistance Initiative (USAI) appropriated by Congress to allow the Biden administration to procure weapons from industry rather than taking weapons from existing U.S. weapons stocks.

Since Russian forces invaded on Feb. 24 in what President Vladimir Putin termed a "special military operation" to demilitarize Ukraine, the conflict has settled into a war of attrition fought primarily in the country's east and south.