U.S. President Joe Biden made a surprise visit to Kyiv ahead of the one-year anniversary of Russia's war on Ukraine to demonstrate Washington's "unwavering" commitment to the Eastern European country.

It was the first time that Biden visited Ukraine since the invasion began on Feb. 24 last year. He met with Ukrainian President Volodymyr Zelenskyy and said that Russian President Vladimir Putin's "war of conquest is failing."

"Putin thought Ukraine was weak and the West was divided," Biden said in the Ukrainian capital. "He thought he could outlast us. I don't think he's thinking that right now."

Biden pledged an additional $500 million worth of military equipment to help protect the Ukrainian people from aerial bombardments.

U.S. President Joe Biden (L) meets Ukrainian President Volodymyr Zelenskyy ahead of the first anniversary of Russia-Ukraine war in Kyiv, Ukraine on Feb. 20, 2023. (Ukrainian Presidency/Anadolu Agency/Getty/Kyodo)

Related coverage:

Japan to invite Ukraine president to G-7 online summit Feb. 24: PM

Prior to the visit, which lasted about five hours, he also released a statement saying that more sanctions against Russia, targeting "elites and companies that are trying to evade or backfill (its) war machine," are due to be announced later this week.

Speaking to the media with Biden, Zelenskyy thanked the U.S. president for visiting Ukraine in "the most difficult time" and said the two leaders discussed a range of issues.

"This conversation brings us closer to the victory," Zelenskyy said.

White House national security adviser Jake Sullivan said it was "unprecedented in modern times" for any U.S. president to visit "the capital of the country at war where the United States military does not control the critical infrastructure."

Sullivan said the trip to Ukraine, before making a scheduled three-day visit to Poland through Wednesday, was decided by Biden, and the United States notified Moscow of the plan shortly before his departure from Washington to prevent any miscalculation.

"One year later, Kyiv stands. And Ukraine stands. Democracy stands," Biden also said after meeting with Zelenskyy at Mariinsky Palace. "The Americans stand with you, and the world stands with you."

During his visit, Biden honored Ukraine's fallen soldiers and held a meeting with U.S. Embassy staff in the war-torn country, in addition to discussing next steps with Zelenskyy.