Sitting next to Scholz in the Oval Office, Biden thanked the German leader for his "strong and steady leadership" and support for Ukraine.
Scholz said it was important to demonstrate that allies would back Ukraine "as long as it takes and as long as is necessary".
Biden hailed Scholz's decision to increase Germany's military spending and diversify energy sources away from Russia and said the two leaders had worked in lock-step with other allies to support Ukraine.
US officials said Ukraine was bracing for a new Russian offensive in coming weeks.
"As NATO allies, we're making the alliance stronger," Biden said, as the US announced a new military aid package for Ukraine worth $US400 million ($A591 million) that includes ammunition and tactical bridges to move tanks and armoured vehicles.
White House press secretary Karine Jean-Pierre told reporters just before the meeting it would help the leaders discuss co-ordination on Ukraine and deepen their relationship.
Scholz's came days after Biden's security adviser Jake Sullivan said Biden only sent Abrams tanks to Ukraine in January because Scholz made it a pre-condition for sending German Leopards.
Biden's decision came against his military's advice, Sullivan told ABC News.
Berlin has insisted Biden came to see it was necessary and so the decision was consensual.
Scholz arrived in Washington as the US is consulting allies about imposing sanctions on China if Beijing provides military support to Russia for its war in Ukraine, according to four US officials and other sources.
Neither Washington nor Berlin has evidence of Beijing's providing weapons to Moscow but US officials say they are monitoring the situation closely.
"We haven't yet seen China do anything yet, as it relates to lethal weapons," Jean-Pierre said.
"Every step China takes toward Russia makes it harder for China with Europe and other countries around the world."
A senior European Union official told a separate briefing it would be an "absolute red line" if China provided weapons to Russia and the EU would respond with sanctions.
Germany has typically taken a much less hawkish stance on China, its top trading partner, than the US, but Scholz on Thursday urged China not to provide weapons to Moscow and asked Beijing to pressure Russia to pull back its forces.
Scholz and Biden were also expected to address a dispute over US subsidies for climate-friendly technologies under the US Inflation Reduction Act (IRA) that German and EU officials worry would disadvantage their companies.
The EU official said US and European officials were working on a high-level agreement that would make European minerals eligible for US tax credits, with an announcement possible as early as next Friday when European Commission President Ursula von der Leyen visits the White House.
