Ukrainian President Volodymyr Zelensky is set to give a high-profile virtual address to members of Congress on Wednesday morning as he tries to build pressure on the U.S. and European allies to ramp up their military support of his nation under siege.

Zelensky’s speech will be the second time he’s spoken before members of Congress this month, but the first time he’ll have a chance to make his pitch directly to Americans in a publicly broadcast address.

The speech comes as Russia’s invasion is about to enter its fourth week, sparking a growing humanitarian crisis and the threat of an entrenched, drawn-out war.

“The speech … should continue to elevate the issue in a way that I think will bring additional pressure on not only the administration but I think both political parties here in Congress to do everything possible to help the Ukrainians,” said Sen. John Thune (S.D.), the No. 2 Senate Republican.

“They see it as a righteous cause, the American people do, and are very I think invested in trying to make sure we do everything we can to support the Ukrainian people,” he added.

President Biden signed $13.6 billion in humanitarian and military assistance to Ukraine into law on Tuesday as part of a massive government funding package ahead of Zelensky’s address.

The billions in aid to Ukraine comes after Biden moved last week to ban imports of Russian oil and, in coordination with Western allies, revoke normal trade relations with Russia. That’s all on top of increasingly harsh sanctions against Russian banks, oligarchs and Russian President Vladimir Putin himself that the U.S. and Europe have imposed in the last few weeks.

But Zelensky is likely to press lawmakers to do more to help his country beat back Russian forces.

Zelensky has been making the rounds before Western legislatures, including those of the European Union, United Kingdom and Canada, to plead for more aggressive international actions against Russia’s increasingly brutal attacks on Ukrainian civilians.

Biden has ruled out policing a no-fly zone over Ukraine or delivering weapons directly, warning that any direct clashes with Russian troops would lead to a “World War III.”

Yet in a likely preview of his message to lawmakers and the American public, Zelensky, in stark terms, urged members of the Canadian parliament on Tuesday to back a no-fly zone over his country.

"Can you imagine when you call your friends, your friend, a nation, and you ask, 'Please close the skies. Close the airspace. Please stop the bombing.' How many more of those missiles have to fall on our cities until you make this happen?" Zelensky asked members of the Canadian parliament.

Lawmakers acknowledged they were skeptical about how Zelensky, a former actor who was elected to be Ukraine’s president in 2019, would respond to a potential Russian invasion, questioning if he would be like former Afghan president Ashraf Ghani, who quickly fled Afghanistan last summer as U.S. troops withdrew from the country and the Taliban closed in on the capital.

But Zelensky has garnered widespread bipartisan praise for his response to Putin’s invasion, vowing to stay in Ukraine, providing social media updates on his talks with other world leaders and providing video updates to rally his citizenry.

“I'm glad he's doing this. I think this is really reaching out to the family of nations that want to see him survive and succeed,” Sen. Dick Durbin (Ill.), the No. 2 Senate Democrat and co-chair of the Senate Ukraine caucus.

Sen. Ben Cardin (D-Md.), a senior member of the Foreign Relations Committee, added that “it’s great to have him here.”

“It’s to show America and the world the courage of Mr. Zelensky that he’s standing up not just for Ukraine but the world and this platform is available to him as a sign of our solidarity,” Cardin said about the speech.

Lawmakers are currently negotiating legislation to revoke normal trade relations with Russia, following Biden’s announcement Friday. They could also fold in elements of a bill that passed the House last week that slapped new sanctions on Moscow and called for condemning the invasion through the World Trade Organization.

But there are divisions within Congress about how far to go to bolster U.S. military aid to Ukraine.

Lawmakers are broadly opposed to creating a no-fly zone — warning that enforcing it would put the United States in direct conflict with Putin.

But members of both parties are now pushing for the administration to help facilitate the transfer of planes from Poland to Ukraine and provide other air defense systems.

“Russia’s advantage in this domain could soon develop into air dominance if the Ukrainians do not receive necessary military aid,” the 58-member Problem Solvers Caucus, which has equal numbers of Democrats and Republicans, said in a statement. “With Russia’s alarming disregard for Ukrainian civilian casualties, the U.S. must also help supply more comprehensive air defense systems to defend Ukraine and its people.”

Thune predicted that Zelensky would ask Congress during his speech for more military aid, including the planes.

“I don’t know why we wouldn’t. This should be an all-out, all-hands-on-deck effort to give them everything that they need,” he said.

But the administration has warned that a plan to give the planes to the United States and then have the United States fly the planes to Ukraine isn’t “tenable” because it escalated the risk of a conflict between NATO and Russia.

“This is a dilemma,” Durbin said about the planes. “It’s a classic dilemma. We want to provide the equipment that Ukraine needs to survive. We don’t want to push Putin into World War III or a nuclear confrontation.”

There’s also the humanitarian element of the crisis for Congress to consider.

Speaker Nancy Pelosi (D-Calif.) predicted that lawmakers would likely take up more assistance for the millions of Ukrainian refugees fleeing the war-torn country beyond what’s already enacted in the legislation Biden signed Tuesday.

“We'll have to do more in terms of meeting the needs of some of the 2.7 million refugees now. 2.7 million,” Pelosi said. “It's a number that is almost incomprehensible and not finished yet. Sad to say.”