Ukrainian President Volodymyr Zelensky is again pushing the United States to take a more aggressive stance against Russia, urging his US counterpart to completely isolate the Russian economy after earlier demanding he impose a no-fly zone over Ukraine.

In his latest call with President Joe Biden last Friday, Zelensky reportedly asked Washington to close any loopholes in existing penalties, to “significantly broaden” the sanctions blacklist for Russian officials and even restrict Moscow’s access to major international waterways. 

The White House has yet to confirm what was discussed on the call, but Biden took additional steps to isolate Russia on the same day, imposing penalties similar to those targeting North Korea and Cuba. It is unclear, however, if the White House will be willing to interfere with Russian ships, as Moscow is liable to see the move as an act of war. 

Though Zelensky was frequently critical of Biden prior to Russia’s invasion in late February – vacillating between slamming the president for both over-hyping and understating that threat Moscow posed – he has since switched his messaging, now demanding more Western involvement in Ukraine as Russian troops capture major cities and close in on its capital. 

Kiev’s major requests have involved air support, even going as far as to urge NATO to establish a no-fly zone over Ukraine. When that was denied over concerns it could spark a third World War, Zelensky asked the bloc to donate warplanes so Ukraine could reestablish control over its airspace. Biden has firmly rejected both requests, while the Pentagon has concluded that a prior plan to transfer Polish MIG-29s to Ukraine would yield little benefit. 

Zelensky is set to appear before Congress by video later in the week, where he is likely to again request additional American support. Ukraine has spent heavily on lobbying legislators in recent years and the president will surely have a receptive audience, with House Speaker Nancy Pelosi saying lawmakers are “thrilled” about the address.