The New York Times says the U.S. proposal would amount to a quarantine of North Korea, although administration officials are not using that word.
(In its editions today / Monday,) The newspaper cites several American and Asian officials as saying the main purpose of the move would be to give China political cover to police its border with North Korea.
The Chinese-North Korean border reportedly is now largely open to shipments of arms, drugs and counterfeit currency -- North Korea's main source of hard currency.