President Trump cited an “unusual and extraordinary threat” to U.S. national security as he acted Friday to maintain long-standing economic restrictions on North Korea, including the freezing of any assets in the United States.

The official declaration, contained in a notice to Congress, came despite Trump’s assertion this month that his historic summit with North Korean leader Kim Jong Un ended the North’s nuclear weapons threat.

“Sleep well tonight!” Trump tweeted June 13, the day after he and Kim met in Singapore.

Harsh economic restrictions will continue for one year under the order Trump signed Friday. The paperwork keeps in place restrictions first imposed a decade ago by President George W. Bush. The ban on the transfer of any U.S. assets by North Korea’s leaders or its ruling party has been extended or expanded several times by both President Barack Obama and Trump himself, in response to North Korean missile tests and other actions.