WASHINGTON — The White House announced on Monday that the United States would send another $550 million in arms to Ukraine to help it fend off Russian invaders, increasing the total American investment in war fighting there to more than $8 billion since the invasion began in February.

President Biden authorized the latest package as the first cargo ship of food finally left the Ukrainian port city of Odesa after months of Russian blockade, in accordance with an agreement with Moscow. The White House called on the Kremlin to continue abiding by the pact in order to ease a growing food crisis around the world.

“Russia has, of course, weaponized food,” said John F. Kirby, a spokesman for the National Security Council. “We urge Russia to meet its commitments under this new arrangement.”

Mr. Kirby said that Secretary of State Antony J. Blinken; Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff; and Jake Sullivan, the national security adviser, had informed their Ukrainian counterparts about the new weapons shipments on Monday. Mr. Blinken said in a statement that he was authorizing a drawdown of arms and equipment from Department of Defense inventories for Ukraine’s self-defense.