Chinese assistance in pressuring North Korea has “not worked out,” President Donald Trump said on Tuesday, a day after it emerged that U.S. national Otto Warmbier had died following his return from imprisonment in the North.

“While I greatly appreciate the efforts of President Xi & China to help with North Korea, it has not worked out. At least I know China tried!” Trump said in a Tweet on Tuesday afternoon.

The remarks, suggesting frustration with Chinese pledges to do more to pressure the North, follow comments the same day in which Trump referred to the death of Warmbier as a “total disgrace” and said it was something that should have