Watch: air raid sirens in Kyiv during Joe Biden's Ukraine visit

U.S. President Joe Biden made an unannounced visit Monday to Ukraine to meet with President Volodymyr Zelenskyy, a gesture of solidarity that comes days before the one-year anniversary of Russia’s invasion of the country.

Footage captured by The Associated Press showed how Biden was given brief firsthand experience of the terror that Ukrainians have lived with for close to a year, as air raids sirens howled over the capital just as he and Zelenskyy were exiting the gold-domed St. Michael’s Cathedral, which they visited together.

Looking solemn, they continued unperturbed as they laid a wreath and held a moment of silence at the Wall of Remembrance honouring Ukrainian soldiers killed since 2014.

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

In Kyiv, Biden announced an additional half-billion dollars in U.S. assistance, including shells for howitzers, anti-tank missiles, air surveillance radars and other aid, but no new advanced weaponry.

Biden’s mission with his visit to Kyiv, which comes ahead of 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 U.S. and allied support for providing weaponry and direct economic assistance has started to soften.

For Zelenskyy, the symbolism of having the U.S. president stand side by side with him on Ukrainian land as the anniversary nears is no small thing as he prods the U.S. and European allies to provide more advanced weaponry and to step up the pace of delivery.