WATCH: White House press secretary Jen Psaki speaks on Biden’s condemnation of Putin

White House press secretary Jen Psaki says President Joe Biden was speaking “from his heart” when he described Russian President Vladimir Putin as a war criminal.

Watch the briefing in the player above.

Biden called Putin a war criminal as the atrocities in Ukraine mount and the president there is begging the U.S. Congress for more help.

“He is a war criminal,” the president said of Putin as he left an unrelated event.

It’s the sharpest condemnation yet of Putin and Russian actions by a U.S. official since the invasion of Ukraine.

Psaki also told reporters the White House understood the appeals of President Volodymyr Zelensky for the U.S. Congress to do more to help Ukraine’s fight against Russia.

Livestreamed into the U.S. Capitol complex Wednesday morning, Zelensky said the U.S. must sanction Russian lawmakers and block imports.

WATCH: ‘We need you right now,’ Ukraine’s Zelensky asks Congress for more help

Lawmakers gave him a standing ovation, before and after his short remarks, which Zelensky began in Ukrainian through an interpreter but then switched to English in a heartfelt appeal to help end the bloodshed.

Nearing the three-week mark in an ever-escalating war, Zelensky is using the world’s leading legislative bodies as a stage to implore allied leaders to stop the Russian airstrikes that are devastating his country.

Psaki said dialogue was continuing with Russia, noting that White House national security adviser Jake Sullivan has spoken to his Russian counterpart, Nikolai Patrushev.

“We requested this call to clearly lay out our commitment to continuing to impose costs on Russia, if they do not stop attacking Ukrainian cities and towns, and to warn them about the consequences and implications of Russia potentially using chemical or biological weapons in Ukraine,” she said.

As Biden prepares to head to Brussels next week, Psaki said he’ll be “meeting with our NATO allies to coordinate our deterrence and defense,” and will discuss where things are on the ground in Ukraine.