The U.S. said Americans should avoid traveling to Japan, with the country under a state of emergency over a widening COVID-19 outbreak that has sown doubts about Tokyo’s plans to host the Olympics in less than two months.

The U.S. State Department raised its travel advisory to level four on Monday, putting Japan in a category with a broad swath of nations from Latin America to Europe that Americans are urged to avoid due to coronavirus concerns. The action is a fresh blow to a country struggling to convince its own public and the international community that it’s ready to host the Summer Olympics beginning on July 23, following their delay in 2020.

Japan’s coronavirus cases are rising largely because it has been slow with its vaccine rollout. Just over 3% of the island nation’s population has been inoculated, the lowest among the 37 members of the Organization for Economic Cooperation and Development, according to Bloomberg’s vaccine tracker. That compares with more than 40% in the U.S. and in the U.K.

Japanese Prime Minister Yoshihide Suga this month extended a state of emergency that covers Tokyo and expanded it to two more regions hit by rising virus cases, in an attempt to stem infections ahead of the Olympics.

The latest COVID-19 wave has largely been driven by more infectious strains from abroad, adding to concerns about inviting thousands of overseas participants, including athletes and officials.

Initially, 600,000 fans from abroad had been projected to attend, but organizers ruled out that possibility in March. Organizers are set to decide soon if even local spectators will be allowed to watch the competitions in person. They already have reduced the number of officials and others expected to attend from overseas to about 78,000, not including athletes.

Some foreign athletes have expressed safety concerns, with the U.S. track and field team canceling pre-Olympics training in the country.

Japan began its immunization effort with health-care workers after the Pfizer Inc.-BioNTech SE vaccine was approved in February. Progress has since been hindered by a conservative medical culture, with local safety trials required before vaccines could be approved and only doctors and nurses allowed to administer shots. A law giving responsibility for inoculations to local municipalities and the testing of a new online reservation system have added to delays.

Japan last week finally approved vaccines developed by Moderna Inc. and AstraZeneca Plc, and the pace of inoculation has picked up to almost 500,000 doses administered daily. That’s still behind the one million goal set by Suga.

The Japanese Consulate General in New York didn’t immediately reply to a request for comment on the U.S. move.