The White House gave Russia 'hours' notice that Joe Biden was making a surprise trip to Ukraine

• President Joe Biden warned Russia before departing for Ukraine on Monday, the White House said.
• National security advisor Jake Sullivan said Moscow was given "hours" notice before the surprise visit.
• Biden's unannounced trip comes just before the one-year anniversary of Russia's unprovoked invasion of Ukraine.

The White House gave Russia "hours" notice that President Biden was visiting Ukraine on Monday, according to national security advisor Jake Sullivan.

Sullivan told reporters that Moscow was notified about Biden's plans just before he left. The heads-up was for "de-confliction purposes," Sullivan said, though he didn't specify who at the Kremlin was contacted or how.

Biden's visit with Ukrainian President Volodymyr Zelenskyy was otherwise announced and came as a surprise to media outlets as well as onlookers.

Biden said Monday that the US would continue to support Ukraine in its fight against Russia, and committed to give $500 million more in military aid to Zelenskyy's forces.

The US president's trip comes just days ahead of the one-year anniversary of Russian President Vladimir Putin's unprovoked invasion of Ukraine.

Ukrainian officials warned last week that Moscow could step up offensive efforts in the coming days, and Kyiv's National Security and Defense Council chief cautioned that the country "must maintain maximum calm."