Earlier Wednesday, Zelenskyy met with President Joe Biden at the White House.
Ukraine's President Volodymyr Zelenskyy made a dramatic visit to Washington Wednesday -- his first known trip outside Ukraine since the Russian invasion began in February.
He met with President Joe Biden at the White House and later addressed Congress as lawmakers are set to vote on $45 billion more in emergency aid as part of a larger spending package. Biden on Wednesday also announced the U.S. will send Ukraine a Patriot anti-missile battery to defend against devastating Russian attacks.
In a virtual address to U.S. lawmakers back in March, Zelenskyy emotionally pleaded for more aggressive measures to help fight the war. Invoking key American tragedies, including Pearl Harbor and the Sept. 11 attacks, Zelenskyy told members at the time, "Just remember it … Our country experiences the same every day right now."
Presiding over the House chamber, Speaker Nancy Pelosi wore a blue suit with a broach -- the "Order of Olga the Duchess of 3rd Degree," a Ukrainian civil decoration given to her by Zelenskyy when she was in Kyiv, her office said.
Pelosi visited Ukraine in May, marking the first official congressional delegation since Russia invaded.
Here is some early color ahead of Zelenskyy's scheduled 7:30 p.m. remarks to a joint meeting of Congress:
The mood is good inside with members mingling. Early attendees included incoming House Minority Leader Hakeem Jeffries, D-N.Y., and Republican Reps. Matt Gaetz of Florida and Lauren Boebert of Colorado.
Gaetz has been one of the most vocal critics in Congress of future Ukraine funding, vowing a few weeks ago not to support additional money.
Some members are wearing yellow scarves and yellow suit jackets -- an apparent reference to solidarity with Ukraine.
Shortly ahead of Zelenskyy's address, House Speaker Nancy Pelosi welcomed senators to the House chamber for the joint meeting, including Vice President Kamala Harris, president of the Senate.
Wyoming Republican Rep. Liz Cheney was seated on the Democrats' side of the House chamber next to lawmakers she served with on the Jan. 6 committee.
-ABC News' Will Steakin
The big four -- House Speaker Nancy Pelosi, Senate Majority Leader Chuck Schumer, Republican Senate Leader Mitch McConnell and House Republican Leader Kevin McCarthy -- met behind closed doors with Zelenskyy ahead of his address to Congress.
Zelenskyy was spotted walking through Statuary Hall outside the House chamber with Pelosi, Schumer and McConnell, but McCarthy, the likely incoming House speaker, was not with them for that walk.
McCarthy, also needing to win over conservatives to back his bid for speaker, has signaled he could oppose more funding to Ukraine, warning that Republicans will not write a "blank check" for aid when they soon assume the majority.
Some conservative House Republicans have made it clear they would oppose any additional funding even as Congress votes on a must-pass $1.7 trillion government funding bill this week that includes $45 billion in aid to Ukraine.
-ABC News' Katherine Faulders and Lauren Peller
President Biden defended the decision to send a Patriot missile defense system to Ukraine and denied the move was escalatory.
"It's a defensive system. It's a defensive weapon system. It's not escalatory, it's defensive," Biden said. "We'd love to not have them use it. Just stop the attacks," he said, referring to Russia.
Zelenskyy delicately added that he may call on the U.S. to send another Patriot missile in the near future, prompting laughter.
"We're working on it," Biden said with a smile.
Zelenskyy said, "We are in war. I'm sorry. I'm really sorry. That is my appreciation."
