STORY: The United States also promised to deploy "strategic assets" - which typically include long-range bomber aircraft, missile submarines, or aircraft carriers - if necessary to deter North Korea.
Biden said Washington had offered COVID-19 vaccines to China and North Korea, which is combating its first acknowledged outbreak. "We've got no response," Biden said.
North Korea reported more than 200,000 new patients suffering from fever for a fifth consecutive day on Saturday, but the country has little in the way of vaccines or modern treatment for the pandemic.
Biden and Yoon Suk-yeol said their countries' decades-old alliance needed to develop not only to face North Korean threats but to keep the Indo-Pacific region "free and open" and protect global supply chains.