"Joseph Biden, welcome to Kyiv! Your visit is an extremely important sign of support for all Ukrainians," Ukraine President Vlodymyr Zelenskyy said on Telegram.
Air raid sirens rang out across the capital as Biden met Ukrainian President Volodymyr Zelenskyy on what is the US president's first visit to the country since Russian troops invaded on February 24, 2022.
The United States gave a heads up to Moscow "hours" ahead of President Joe Biden's surprise trip to avoid any chance of conflict, a senior White House aide said.
"We did notify the Russians that President Biden will be traveling to Kyiv. We did so some hours before his departure for deconfliction purposes," National Security Advisor Jake Sullivan told reporters. "Because of the sensitive nature of those communications, I won't get into how they responded or what the precise nature of our message was."
In Kyiv, Biden and Zelenskyy walked over and together laid a wreath at the Wall of Remembrance for the fallen heroes of the Russian-Ukrainian war, as a military salute played and the two presidents stared down in silence for a few moments.
Biden promised increased arms deliveries for Ukraine and vowed Washington's "unflagging commitment" in defending Ukraine's territorial integrity.
"I will announce another delivery of critical equipment, including artillery ammunition, anti-armor systems, and air surveillance radars to help protect the Ukrainian people from aerial bombardments," he was quoted as saying in a White House statement.
Ukraine is estimated to be burning through thousands more shells each month than the EU defense industry is currently able to produce.
Zelenskyy hailed Biden's visit as a key sign of support.
Ukrainian President Volodymyr Zelenskyy on Monday said Russia did not stand a chance of winning its war, after US leader Joe Biden promised additional arms supplies on a surprise visit to Kyiv.
"This is an unequivocal signal that Russian attempts to win will have no chance," he said, referring to Biden's visit and new pledges of military support. "Together we will protect our cities, our people from the terror of Russia."
The visit came as Beijing lashed out against US claims that China was considering sending arms to Russia to assist in its war in Ukraine.
"It is the United States and not China that is endlessly shipping weapons to the battlefield," China's foreign ministry spokesman Wang Wenbin said when asked about the US claims.
"We urge the United States to earnestly reflect on its own actions, and do more to alleviate the situation, promote peace and dialogue, and stop shifting blame and spreading false information," he told a regular briefing.
The EU's foreign policy chief Josep Borrell also warned China against providing Russia with weapons for the war in Ukraine, saying: "for us, it would be a red line in our relationship."
"We'll do everything we can," Borrell said. "This is the most urgent issue, if we fail on that then really the result of the war is in danger."
At the Munich security conference over the weekend, Borrell issued a stark warning about Ukraine's dwindling supplies of bullets and similar munitions as it fights back against Russia's invasion.
"(Let's) accelerate our military support to Ukraine because Ukraine is in a critical situation from the point of view with ammunition available," Borrell said.
"This shortage of ammunition has to resolve quickly, it's a matter of weeks."
Biden will speak in Warsaw on Tuesday to hail NATO's unprecedented effort to help Ukrainians save their country as he marks the war's first year.
On the same day, President Vladimir Putin is set to give his own speech in Moscow, three days from the February 24th anniversary of Russian tanks rolling into Ukraine.
Japanese Prime Minister Fumio Kishida said Monday he would host an online meeting between Group of Seven leaders and Ukrainian President Volodymyr Zelenskyy on Friday - a year to the day since Russia invaded.
"So the G7 leaders can remain united to deal with the invasion of Ukraine, I have decided to host a video conference of the G7 leaders, inviting President Zelenskyy, this week on the 24th," Kishida said in a speech in Tokyo.