U.K. Prime Minister Rishi Sunak is to announce a $617-million aid package for Ukraine -- Britain's largest ever -- on a visit to Poland on April 23, the British government said in a statement. "Ukraine is facing an existential threat as Russia continues its barbaric invasion, risking the security and stability of all of Europe," the statement said. Britain has been one of Ukraine's staunchest supporters. The extra funding brings the U.K.'s total military aid for this financial year to $3.71 billion. Britain will also send what it said is its largest-ever single package of equipment, the statement added.