Joe Biden walks with Volodymyr Zelenskyy at St. Michaels Golden-Domed Cathedral during an unannounced visit, in Kyiv, Ukraine, on Monday. AP

President Joe Biden swept unannounced into Ukraine on Monday to meet with President Volodymyr Zelensky in a defiant display of Western solidarity with a country still fighting what he called "a brutal and unjust war” days before the first anniversary of Russia’s invasion.

"One year later, Kyiv stands,” Biden declared after meeting Zelensky at Mariinsky Palace.

Jabbing his finger for emphasis on his podium, against a backdrop of three flags from each country, he continued: "And Ukraine stands. Democracy stands. The Americans stand with you, and the world stands with you.”

Biden spent more than five hours in the Ukrainian capital, consulting with Zelensky on next steps, honoring the country’s fallen soldiers and seeing US embassy staff in the besieged country.

 An air raid sirens blared across the Ukrainian capital as Biden visited Kyiv but there were no reports of Russian missile or air strikes.

The visit comes at a crucial moment: Biden is trying to keep allies unified in their support for Ukraine as the war is expected to intensify with spring offensives.

Zelensky is pressing allies to speed up delivery of promised weapon systems and calling on the West to provide fighter jets - something that Biden has declined to do.

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The US president got a taste of the terror that Ukrainians have lived with for close to a year when air raids sirens howled just as he and Zelensky wrapped up a visit to the gold-domed St. Michael’s Cathedral.

Volodymyr Zelensky and Joe Biden open a plaque with his name on the Alley of Bravery in Kyiv. Reuters

Looking solemn, they continued unperturbed as they laid two wreaths and held a moment of silence at the Wall of Remembrance honoring Ukrainian soldiers killed since 2014, the year Russia annexed Ukraine’s Crimean peninsula and Russian-backed fighting erupted in eastern Ukraine.

The White House would not go into specifics, but national security adviser Jake Sullivan said that it notified Moscow of Biden’s visit to Kyiv shortly before his departure from Washington "for deconfliction purposes” in an effort to avoid any miscalculation that could bring the two nuclear-armed nations into direct conflict.

Joe Biden (left) walks next to Volodymyr Zelensky as he arrives for a visit in Kyiv on Monday. AFP

Ukraine has also been pushing for battlefield systems that would allow its forces to strike Russian targets that have been moved back from frontline areas, out of the range of HIMARS missiles that have already been delivered. Zelensky said he and Biden spoke about "long-range weapons and the weapons that may still be supplied to Ukraine even though it wasn’t supplied before.” But he did not detail any new commitments.

"Our negotiations were very fruitful,” Zelensky added. Sullivan would not detail any potential new capabilities for Ukraine, but said there was a ”good discussion” of the subject.

Biden’s mission with his visit to Kyiv, which comes before a scheduled trip to Warsaw, Poland, is to underscore that the United States is prepared to stick with Ukraine "as long as it takes” to repel

Russian forces even as public opinion polling suggests that US and allied support for providing weaponry and direct economic assistance has started to soften.

Associated Press