Biden makes surprise trip to Kyiv before invasion anniversary

US President Joe Biden on Monday made a trip to Kyiv organised in strict secrecy, promising $500 million in fresh arms deliveries and "unwavering" American support ahead of the first anniversary of Russia's invasion.

Air raid sirens rang out across the capital at one point as Biden walked alongside Ukrainian President Volodymyr Zelensky during what was the US president's first visit to the country since Russian troops invaded on February 24, 2022.

"One year later, Kyiv stands. And Ukraine stands. Democracy stands," Biden said, speaking alongside Zelensky at the Ukrainian president's official residence, the Mariinsky Palace.

"I thought it was critical that there not be any doubt, none whatsoever, about US support for Ukraine in the war," he continued.

Russian President Vladimir "Putin thought Ukraine was weak and the West was divided. He thought he could outlast us."

"He's just been plain wrong," Biden said, adding: "Putin's war of conquest is failing".

The visit was organised in conditions of strict secrecy.

Biden left Andrews Air Force Base in the early hours of Sunday.

After handing over their devices, journalists were made aware of his presence on Air Force One just 15 minutes before the plane took off.

The White House did not report how he eventually reached Ukraine but other foreign leaders have travelled to Kyiv by train from Poland.

It was the first visit by a US president to Ukraine since 2008.

During the trip, Biden promised an additional $500 million (468 million euros) in arms deliveries for Ukraine, mentioning in particular artillery ammunition, howitzers and Javelin anti-tank missiles.

Ukraine is estimated to be burning through thousands more shells each month than the EU defence industry is currently able to produce.

The European Union is weighing up plans to try to speed up its production and delivery of much-needed ammunition to help Kyiv's fight.

Zelensky said he and Biden also discussed the possibility of supplying "long range weapons" to Ukraine, a long-standing request from Kyiv that has been met with reticence in Washington where there is concern that they could be used to strike deep inside Russian territory.

Zelensky hailed the visit as a key sign of support.

"This conversation brings us closer to victory," he said, calling the visit and the promise of additional US arms supplies "an unequivocal signal that Russian attempts to win will have no chance".

After their talks, Biden and Zelensky visited St Michael's Gold-Domed Cathedral, which has long been a symbol of Ukrainian resistance, and the air raid sirens were heard across the city as the two leaders left the church.

Biden and Zelensky then 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 later visited the US embassy in Kyiv before leaving the capital, according to a White House pool report.

He is expected to arrive in Poland on Tuesday where he is due to give a major speech in Warsaw -- hours after a state of the nation address by Putin in Moscow that will be largely about the conflict in Ukraine.

Biden's 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.

According to the latest estimates from Norway, the conflict has wounded or killed 180,000 Russian soldiers and 100,000 Ukrainian troops.

Other Western sources estimate the war has caused 150,000 casualties on each side.