US National Security Advisor Jake Sullivan warned on Tuesday that 2024 would pose significant challenges if the US Congress does not endorse new military aid for Ukraine.

"I think 2024 will be a very difficult year if we are not able to get the assistance to Ukraine," Sullivan told the WSJ CEO Council.

Sullivan cautioned that the inability of Congress to endorse President Joe Biden's national security supplemental request would greatly impact Ukraine's ability to both maintain and reclaim territory from Russian forces.

He stated that if the US falls short in supplying the required quantity of ammunition and weapons systems, Ukraine will be unable to replicate the battlefield advancements witnessed in the past 18 months.

Sullivan to discuss Gaza war timetable with 'Israel'

Elsewhere in his statements, Sullivan said that he plans to engage in discussions with Israeli officials regarding their timeline for the war on Gaza.

In the face of increasing global calls for "Israel" to implement a ceasefire, Sullivan mentioned that the upcoming talks would involve conversations about "Israel's" post-war strategy for Gaza.

Read more: Zelensky pleads for more US aid, amid Republicans' floundering support

Things aren't looking so good for Ukraine as Kiev is losing more men, struggling with raising money, and now facing the prospect of giving up ground.

Ukrainian President Volodymyr Zelensky is set to visit Congress and the White House on Tuesday to seek increased US military assistance.

However, the Republican Party appears largely unresponsive to his growingly urgent appeals. Throughout the nearly two-year war in Ukraine, the United States has spearheaded a Western coalition, providing substantial financial support in the form of weaponry and ammunition.

On Sunday, Republican US Senator JD Vance suggested that in order to bring an end to the Russian operation in Ukraine, there might be a necessity for Ukraine to relinquish territory to Russia.

"What’s in America’s best interest is to accept Ukraine is going to have to cede some territory to the Russians and we need to bring this war to a close," Vance, of Ohio, said on CNN’s State of the Union. "The idea that Ukraine was going to throw Russia back to the 1991 border was preposterous – nobody actually believed it."