US President Joe Biden has stood alongside Ukraine's Volodymyr Zelenskiy at the White House to urge Americans and the world to keep supporting Kyiv in 2023 as the Ukrainian leader made his first foreign wartime visit.
Zelenskiy presented Biden with a Ukrainian medal offered by a captain of a HIMARS rocket unit and expressed gratitude for the US president's role in helping Ukraine and rallying support.
The United States has sent about $US50 billion ($A75 billion) in assistance to Kyiv as Europe's biggest land conflict since World War II drags on, killing tens of thousands of people, driving millions from their homes and reducing cities to ruins.
But some Republicans, who will take control of the House of Representatives next year, have expressed concerns about the price tag, and European countries have suffered due to energy problems and the hit to the global economy.
"As we head into the New Year, it's important for the American people, and for the world, to hear directly from you Mr President about Ukraine's fight and the need to continue to stand together through 2023," said Biden at a news conference on Wednesday.
Biden said he had never seen NATO nor the EU more united than about Ukraine.
"The United States will stand up for our shared values, the values of freedom," said Zelenskiy, wearing his trademark olive green pants and sweater.
"I believe that despite any changes in the composition of Congress, bicameral and bipartisan support will be maintained."
Earlier, Biden and first lady Jill greeted Zelenskiy on the White House lawn before the two leaders spoke at the Oval Office.
Zelenskiy, who will seek more support during the trip, is due to address a joint session of the US Senate and House of Representatives and meet Republican leaders there.
Some in Moscow expected the campaign to achieve a rapid victory. But the conflict is passing its 300-day milestone.
On Wednesday, US Secretary of State Antony Blinken announced the US would provide another $US1.85 billion ($A2.76 billion) in military aid for Ukraine including a Patriot air defence system to help it ward off barrages of Russian missiles.
Ukraine has come under repeated Russian missile and drone strikes targeting its energy infrastructure, leaving millions of people without electricity or running water in the dead of a freezing winter.
The Patriot missile is deemed to be one of the most advanced US air defence systems, offering protection against attacking aircraft as well as cruise and ballistic missiles.
Putin was defiant on Wednesday at an end-of-year meeting of top defence chiefs, saying Russian forces were fighting like heroes in Ukraine, would be equipped with modern weapons and would achieve all Moscow's goals.
Putin said there were no financial limits on what the government would provide in terms of equipment and hardware, but the army had to learn from and fix the problems it had experienced in Ukraine.
He gave his backing to a plan by his defence minister to boost the size of the armed forces by more than 30 per cent to 1.5 million combat personnel.
© RAW 2022