U.S. President Joe Biden on Thursday pledged additional military assistance for Ukraine valued at up to $325 million during talks with the country's President Volodymyr Zelenskyy.

As he met Biden for one-on-one talks in the Oval Office at the White House, Zelenskyy expressed gratitude for all the aid provided by the United States since the start of Russia's invasion of Ukraine and said the purpose of his visit was to "defend Ukrainian children, our families, our homes, freedom and democracy in the world."

U.S. President Joe Biden (center R) welcomes Ukrainian President Volodymyr Zelenskyy (center L) at the White House in Washington on Sept. 21, 2023. (Kyodo) 

Biden's top national security aide Jake Sullivan said the assistance package was designed to especially beef up Ukraine's air defenses ahead of "what is likely to be a tough winter, filled with renewed Russian attacks on Ukrainian critical infrastructure to try to deprive innocent people of necessities like heat and electricity."

According to the U.S. Defense Department, the new package includes additional missiles for air defense, ammunition for HIMARS rocket artillery systems and machine guns to counter drones.

Before starting an expanded meeting later with Cabinet members, Biden told Zelenskyy that "the American people, Democrats and Republicans alike, families all across our nation understand what Ukraine is fighting to defend."

"It's pretty basic. Freedom, liberty, and sovereignty," Biden said. "That's why, together with our allies and partners, we will continue to provide security assistance to support Ukraine's progress in reclaiming its territory."

Biden disclosed in the presence of the press that the first batch of U.S. Abrams tanks will arrive in Ukraine next week.

Biden said he also discussed with Zelenskyy their efforts to promote Ukraine's economic recovery, including ways to generate international private-sector investment in the country.

Zelenskyy said, without elaborating, that they had agreed on "specific steps" to increase grain exports from Ukraine amid the blockade of its Black Sea ports by Russia.

U.S. President Joe Biden (R) meets with Ukrainian President Volodymyr Zelenskyy at the White House in Washington on Sept. 21, 2023. (AP/Kyodo) 

Zelenskyy's visit to the White House, his second since Russia invaded Ukraine in February 2022, came as some U.S. congressional Republicans have increasingly expressed skepticism about spending more to assist the war-torn country.

While Ukraine's slower-than-hoped counteroffensive is struggling to drive out Russian forces, the U.S. administration under Biden, a Democrat who is seeking re-election in 2024, is grappling to secure bipartisan congressional approval for another $24 billion to help Kyiv.

With no immediate end to the war in sight, Biden has, together with Zelenskyy, rallied international support for Ukraine, stressing that its victory is in the interests of the United States and global democracy.

Both leaders continued their efforts during U.N. General Assembly events in New York earlier this week before Thursday's meeting in Washington.

Ahead of his talks with Biden, Zelenskyy met with U.S. lawmakers at the Capitol and U.S. Defense Secretary Lloyd Austin at the Pentagon, explaining the current situation in Ukraine and its war plans, aiming to secure more support.

Since the start of Russia's invasion, the United States has provided more than $43.9 billion in security assistance, according to government officials.

However, the latest aid package funded by money authorized by Congress to last until the end of September did not include long-range Army Tactical Missile Systems, or ATACMS, that Ukraine has requested.

"The president is constantly speaking both to his own military and to his counterparts in Europe and to the Ukrainians themselves about what is needed on the battlefield at any given phase of the war and then what the United States can provide," Sullivan said.

"As he's weighed all that up to date, he has determined that he would not provide ATACMS, but he has also not taken it off the table in the future," the national security adviser added.

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