The State Department raised its travel alert to Level 4 for the entire world, an unprecedented move aimed at keeping Americans from going overseas as the Trump administration tries to get control of the coronavirus.

In a notice Thursday afternoon, the department said Americans who venture abroad may find their travel plans “severely disrupted” and “may be forced to remain outside of the United States for an indefinite timeframe.” Level 4 is the highest advisory in the State Department’s travel alert system and is normally reserved for countries in ‘a state of war such as Yemen and Somalia.

For those already abroad, the department said that “in countries where commercial departure options remain available, U.S. citizens who live in the United States should arrange for immediate return to the United States, unless they are prepared to remain abroad for an indefinite period.”

At the same time, the State Department announced it was severely curtailing passport services for Americans. U.S. citizens will only be able to get passports for a “qualified life-or-death emergency” such as a serious illness or death in the family and need to travel within three days.

After weeks of playing down the coronavirus threat, President Donald Trump has instituted more severe measures in the effort to contain the spread of the virus. Outbreaks have hit most of Europe, and the disease is running rampant in Spain, Italy and Iran. Airlines and the cruise industry have drastically scaled back operations.

Last week, Trump banned almost all citizens of European countries from entering the U.S., and the State Department raised the travel alert to Level 3. The State Department has also authorized American diplomats to leave posts in countries that are in the middle of outbreaks, a fact that the department said may limit embassies’ ability to help U.S. citizens.

Read More: Europe Blindsided by Travel Ban Trump Failed to Brief Allies On

The warning to get home or hunker down overseas is advice most Americans have already heeded—or at least tried to. With airlines around the world canceling flights and some countries closing their borders, thousands of U.S. citizens have found themselves stuck overseas and unable to get home. Some have accused the State Department of ignoring their pleas for help.

Earlier this week, a spokesman said the department’s top priority was Americans’ safety and security but that they shouldn’t rely on the U.S. government to get them home.While the U.S. has barred flights from China and most European nations, and closed the border with Canada to non-essential travel, Americans have continued to fly—although in limited numbers—to other nations that have outbreaks.