The President made this known through a tweet on his twitter page.

He tweeted:

"In light of the attack from the Invisible Enemy, as well as the need to protect the jobs of our GREAT American Citizens, I will be signing an Executive Order to temporarily suspend immigration into the United States!"

However, the tweet did not shows the mechanism he will use to suspend immigration, how long such a suspension could last or what effect this will have on the operation of US border crossings and on those who already hold green cards.