US President Donald Trump on Friday cited “an unusual and extraordinary threat” from North Korea’s nuclear arsenal to extend sanctions on Kim Jong Un’s regime, despite touting the success of a historic June 12 summit.

An official declaration, contained in a notice to Congress, came on Friday despite Trump’s assertion this month that his June 12 historic summit with North Korean leader Kim Jong-un ended Pyongyang’s nuclear weapons threat, reports The Washington Post.

“The existence and risk of proliferation of weapons-usable fissile material on the Korean Peninsula and the actions and policies of the Government of North Korea continue to pose an unusual and extraordinary threat to the national security, foreign policy, and economy of the United States,” the declaration said.

Earlier, after flying back to Washington last week, boasting of success, the US leader had tweeted: “There is no longer a Nuclear Threat from North Korea.” “Sleep well tonight!” he added on June 13, a day after the Singapore meeting.

According to the current media reports, harsh economic restrictions will continue for one year under the declaration 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 American assets by North Korea’s leaders or its ruling party has been extended or expanded several times by former President Barack Obama and Trump himself in response to North Korean missile tests and other actions.

Though the notice is considered pro forma, the disparity in tone reflects the work that US officials concede remains to be done as negotiators thrash out the details of Pyongyang’s disarmament.

At their summit, Kim and Trump had signed a pledge “to work towards complete denuclearization of the Korean Peninsula,” a stock phrase favoured by Pyongyang that stopped short of longstanding US demands for North Korea to give up its atomic arsenal in a “verifiable” and “irreversible” way.

Critics have pointed to the vague wording of the non-binding summit document and raised fears that the summit could weaken the international coalition against the North’s nuclear programme.

(With inputs from agencies)