(Bloomberg) -- Ukrainian President Volodymyr Zelenskiy headed to Washington on his first trip abroad since Russia’s February invasion to reinforce international support as Moscow vowed to spend as much as it takes to win the war. 

Zelenskiy, who had previously declined invitations from foreign leaders, will use his surprise visit to deliver an in-person speech on Wednesday to the US House of Representatives, which will switch from Democratic to Republican control in January.

After months of pleading for more military support, Zelenskiy is keeping pressure on allies to stay focused as the risk of solidarity fatigue grows. With Russian missile bombardments leaving millions of Ukrainians without power and water and the war heading into its 11th month, he’ll press the case for more air-defense, long-range missiles and tanks.

The visit coincides with a debate in the US legislature over nearly $45 billion in new military aid to Ukraine in a sprawling spending bill. President Joe Biden will also announce a plan to give Ukraine a Patriot air-defense system. 

That decision abandons earlier reluctance to provide Kyiv with the advanced system that can target aircraft and incoming missiles and Moscow’s warnings that doing so would escalate tensions with NATO.

“This week is extremely important for Ukraine - in order to get through this winter and next year,” Zelenskiy said in his nightly address on Tuesday after visiting the eastern town of Bakhmut, where the most fierce battles between Ukraine and Russia have raged for months.

Zelenskiy’s visit follows a shift in tactics by Russia, which after suffering repeated losses on the battlefield has turned to bombarding Ukraine’s power grid and other civilian infrastructure with the aim of breaking Ukrainians’ spirit of resistance.

After President Vladimir Putin called up more than 300,000 additional soldiers to fight, he said on Wednesday Russia has “no limitations” on military spending for the war. His defense minister said Russia would expand its army by more than a quarter to 1.5 million men as it pursues its military aims in its former Soviet neighbor Ukraine. 

“The country and government is giving everything that the army asks for — everything,” Putin said in Moscow.

Emotional Appeal

Zelenskiy, a former TV sitcom star, addressed the US Congress in March, with his team assembling a powerful video of Russia’s devastating war.

With the US spearheading NATO members’ efforts to arm Ukraine, he has met virtually with Biden on a regular basis. The last time they sat down in person was in August 2021 at the White House, and the Ukrainian leader met Vice President Kamala Harris in Munich on the eve of the war.

But support may weaken after Republicans, who have been more skeptical of Biden’s assistance to Kyiv, won a majority in the House in the November midterm elections. They’ll take control in January.

“Zelenskiy’s trip to Washington should be a decisive driver to get that military aid Ukraine needs,” Volodymyr Fesenko, head of the Penta research institute in Kyiv, said by phone. “He’s expected to give an emotionally-political impetus to Congress to approve this crucial decision.” 

Zelenskiy’s administration is also seeking the US Army Tactical Missile System (ATACAMS), a long-range guided missile with a maximum range of 300 kilometers (180 miles). As with the Patriot system previously, the US rejected the plea over concerns Russia may escalate. 

But with Ukrainian officials warning that Putin’s forces may be preparing for a new strike at Kyiv, Zelenskiy may argue that more powerful weapons are needed now to score a decisive victory.

“Winter and spring will be a crucial period of this war,” said Fesenko. “It will determine whether this war ends next year or drags on.”    

--With assistance from Olesia Safronova.

©2022 Bloomberg L.P.