The US State Department on Thursday issued its highest-level travel advisory for every country, essentially warning against any travel abroad.

The move comes as countries try to contain the spread of the novel coronavirus, which has infected more than 227,000 people and killed more than 9,300 people worldwide.

Americans currently abroad were advised to return to the US quickly or plan to shelter in place. The State Department said Americans who did not return immediately should be "prepared to remain abroad for an indefinite period."

Citing unnamed sources, Politico reported earlier on Thursday that a blanket "Level 4" travel advisory would soon be applied to all international travel.

Under the State Department's advisory system, Level 4 means "do not travel." While it is not a legal prohibition, it is considered a stringent warning of life-threatening hazards and is typically reserved for war zones and countries with uncontained dangerous situations, like disease outbreaks or financial collapse.

The department says a Level 4 advisory means that "during an emergency, the U.S. government may have very limited ability to provide assistance." Before the blanket advisory on Thursday, 16 countries had Level 4 advisories, including Afghanistan, Syria, Libya, Iran, and China.

The State Department did not immediately return a request for comment.

This story has been updated with confirmation of the advisory news previously reported by Politico.