(Bloomberg) — President Donald Trump said he’ll sign an executive order temporarily suspending immigration into the United States as the country tries to contain the spread of the coronavirus.

Trump made the announcement by tweet late Monday night, and did not offer specifics, such as the time frame or the scope of who would be affected. The White House did not immediately respond to a request for comment.

He tweeted that he made the decision, “in light of the attack from the Invisible Enemy, as well as the need to protect the jobs of our GREAT American Citizens.”

The president has often said the pandemic has strengthened his desire to further restrict access to the U.S. He has imposed travel restrictions widely to curb the virus’s spread, including on China, Europe, Canada and Mexico. Trump’s Gallup approval rating slipped six points last week as scrutiny of his handling of the outbreak has intensified.

Cracking down on illegal immigration and a promise to erect a wall at the Mexican border formed the centerpiece of Trump’s election campaign in 2016.

Since becoming president, he has sought to curb immigration and migration widely — restricting travel from certain majority-Muslim nations, pushing to erect the wall, striking deals to almost immediately deport asylum seekers from certain countries and moving to slash the number of refugees that the U.S. accepts.