Ukraine President Volodymyr Zelenskyy is expected to address U.S. senators Tuesday during a classified briefing. 

The briefing, which will include secretaries of Defense, State and other top national security officials, comes as the Biden administration has been pushing Congress to pass a $106 billion aid package for the wars in Ukraine, Israel, and other security needs. 

Senate Majority Leader Chuck Schumer on Monday highlighted the need for further assistance to Ukraine, saying Kyiv’s war effort to defend itself from Russia’s invasion may grind to a halt without it.

Office of Management and Budget Director Shalanda Young has also warned lawmakers that the U.S. will run out of funding to send weapons and assistance to Ukraine by the end of the year.

But Biden’s $106 billion aid request is facing deep skepticism from GOP lawmakers wary about continued support of Ukraine’s war efforts at the expense of the U.S.-Mexico border. 

Many Republicans supportive of the funding are insisting on border policy changes to halt the flow of migrants as a condition for the assistance.

Negotiations over the border security package broke down over the weekend as Republicans insisted on provisions that Democrats dismissed as Draconian, such as pressing for ‘indefinite detention’ of asylum seekers and granting the executive branch power to ‘shut down’ the asylum system. Talks are expected to resume this week.

Congress already has allocated $111 billion to assist Ukraine, including $67 billion in military procurement funding, $27 billion for economic and civil assistance and $10 billion for humanitarian aid. Young wrote that all of it, other than about 3% of the military funding, had been depleted by mid-November. 

Meanwhile, the GOP-controlled House has passed a standalone assistance package for Israel as it fights the war with Hamas in Gaza, while the White House has maintained that all the priorities must be met.

The new package proposes an additional $61 billion for Ukraine, $14.3 billion for Israel, which includes $10.6 billion for weaponry, nearly $14 billion for border security, along with aid for the Asia-Pacific region and other U.S. national security provisions.

House Speaker Mike Johnson reiterated Monday that House Republicans will insist on border policy changes as part of a Ukraine assistance bill. He argued Biden has ‘failed to substantively address any of my conference’s legitimate concerns about the lack of a clear strategy in Ukraine, a path to resolving the conflict, or a plan for adequately ensuring accountability for aid provided by American taxpayers.’

Schumer is expected to push forward Biden’s supplemental funding package this week, but Republicans are threatening to block its passage with a filibuster as they insist on border security provisions.

The Associated Press contributed to this report.