In short:
Outgoing US President Joe Biden has directed the country's Department of Defense to continue delivering weapons to Ukraine.
The commitment is part of an ongoing $280.4 billion aid deal for Ukraine and comes after Russia launched missile strikes against Ukraine on Christmas Day.
What's next?
US President-elect Donald Trump will be sworn into office on January 20 and has repeatedly claimed he could end Russia's war with Ukraine 'within 24 hours'.
Outgoing United States President Joe Biden has directed the country's Department of Defense to continue delivering weapons to Ukraine, on the same day Russia launched a Christmas missile attack on Ukrainian energy infrastructure in multiple cities.
The strikes targeted power stations in the north-eastern Ukrainian city of Kharkiv and the south-eastern Dnipro region killed at least one person and injured six more as the country woke on Christmas Day.
In the aftermath of the missile strikes, half a million people in the Kharkiv region were left without heating in temperatures just a few degrees Celsius above zero, while there were blackouts in the capital Kyiv and elsewhere.
President Biden condemned the attack on Wednesday as "outrageous" and said the US will "continue to work tirelessly to strengthen Ukraine’s position in its defence against Russian forces."
Outgoing US President Joe Biden, pictured here with Ukrainian President Volodomyr Zelenskyy in June, has committed to maintaining his country's delivery of military weapons to Ukraine. (Reuters: Kevin Lamarque)
"The purpose of this outrageous attack was to cut off the Ukrainian people's access to heat and electricity during winter and to jeopardise the safety of its grid," Mr Biden said.
"Let me be clear: the Ukrainian people deserve to live in peace and safety.
Kharkiv targeted in 'massive' missile attack, Ukraine authorities say
Photo shows Two people stand amid a pile of debris
"The United States and the international community must continue to stand with Ukraine until it triumphs over Russia's aggression."
The president's commitment to further weapons deliveries to Ukraine come less than a month before President-elect Donald Trump is sworn into office on January 20.
Washington has already committed $US175 billion ($280.4 billion) in aid for Ukraine. It is not certain whether that flow will continue at that pace under Trump.
Prior to his victory in this year's US election, Trump repeatedly claimed that he could end the almost three-year war being waged between Ukraine and Russia "within 24 hours".
Cities and regions across Ukraine came under fire from ballistic missiles launched by Russia in the early hours of Christmas Day. (Reuters: Sofiia Gatilova)
Mick Ryan, a retired major general in the Australian Army, told ABC News on Thursday that Trump's vision to end the war "is a fantasy".
"I think we all know there is zero chance of ending the war on the first day he comes into power," Mr Ryan said.
"He will find once he comes into office, with all the additional intelligence briefs he gets, that it will be a far more difficult proposition.
"Forcing the Ukrainians into a quick peace doesn't mean it will be an enduring or just peace."
Concerns have previously been raised that the second Trump presidency could see Ukraine forced into accepting an unfavourable peace deal and relinquishing land currently occupied by Russian forces.
Russia currently occupies around 20 per cent of Ukraine and has said it will not end the war until its annexations are recognised, including the areas of Crimea, Donbas and the Zaporizhzhia and Kherson regions.
That includes Crimea, which Moscow annexed from Ukraine in 2014, about 80 per cent of the Donbas and more than 70 per cent of the Zaporizhzhia and Kherson regions.
Ukranian emergency authorities scrambled to respond to the Russian strikes, which targeted energy infrastructure across the country. (Reuters: State Emergency Service of Ukraine)
Russia's 'Christmas gift to Ukraine weaponises winter'
In the hours after Russia's ballistic strikes on Ukraine, President Volodymyr Zelenskyy said that more than 70 missiles had fallen and more than 100 drone attacks had been reported across the country.
Ukrainian authorities said more than 70 missiles were launched and more than 100 drone attacks reported in the strikes that caused significant damages to buildings. (AP: Ukrainian Emergency Service)
"Today, Putin deliberately chose Christmas to attack. What could be more inhuman?" Mr Zelenskyy said in a statement on Wednesday.
"Russian evil will not break Ukraine and will not ruin Christmas."
Russia's Defence Ministry later confirmed it had conducted a "massive strike" on critical energy facilities, and heralded the attacks as a victory.
The largest private energy provider in Ukraine, DTEK, also said that the attacks had targeted its electricity generation facilities and the missile had left power equipment with serious damages.
Donald Trump says he could end the Ukraine war 'in 24 hours', but Russia disagrees
Photo shows Vladimir Putin, wearing a dark suit, sits behind a microphone holding pieces of paper.
"We appeal to every ally of Ukraine to end this state-sponsored terrorism now by giving our armed forces the air defence ammunition they need to protect essential energy infrastructure," DTEK CEO Maxim Timchenko said in a statement.
"Denying light and warmth to millions of peace-loving people as they celebrate Christmas is a depraved and evil act that must be answered."
The US Ambassador in Ukraine, Bridget Brink, was equally as scathing in her rebuke of the Christmas attacks.
"Russia's Christmas gift to Ukraine: more than 70 missiles and 100 drones, directed at Ukrainian families celebrating in their homes and the energy infrastructure that keeps them warm," Ms Brink said.
"For the third holiday season, Russia weaponises winter."
In the hours after the strikes, authorities in Kyiv said that a Russian missile had flown through airspace over Moldova and Romania.
Romanian authorities said no violation was detected, but officials in Moldova confirmed later on Wednesday that a missile had been seen.
"Russia deliberately flew these devices at a very low altitude to avoid detection", a Moldovan presidency spokesperson told AFP.
Russia meanwhile said five people had died in Ukrainian strikes and from a falling drone in the border region of Kursk and in North Ossetia in the Caucasus.
'Terror is the objective': Army veteran
Major General Ryan told ABC News that Russia's Christmas strikes on Ukraine were "more than callous" and demonstrates that the Kremlin "only wants peace on its own terms".
"[Russia] has several objectives, none of them good and none of them consistent with the laws of war," he said.
"Firstly, to terrorise the people of Ukraine. That's been a consistent objective of these attacks throughout the war.
"Secondly, to put political pressure on the Ukrainian president and, finally, to continue projecting into the minds of the incoming Trump administration that they should quickly force Ukraine into a peace deal with Russia.
"Russia only wants peace on its terms. I think it will be a very difficult one to negotiate."
ABC/Wires