“The answer is yes we’ve offered vaccines, not only to North Korea but to China as well,” Biden said at a joint press conference in Seoul with the South Korean president. “And we’re prepared to do that immediately. We’ve gotten no response.”

North Korea has long been isolated from the rest of the world, and the secretive government did not report any coronavirus cases for much of the first two years of the pandemic. But in recent weeks, the country has seen an outbreak of hundreds of thousands of cases and dozens of deaths from the virus, according to state media, triggering concern from the international community given North Korea’s limited access to outside medicine and its fragile health care system.