"We had good intelligence before the launch and good intelligence after the launch," the adviser told reporters on condition of anonymity.
South Korea, which hosts 28,500 U.S. troops, warned of punitive action if the launch led to further provocations.
China banned all imports of North Korean coal on Feb. 26, cutting off the country's most important export product.
Sinpo, where the Sunday launch took place, is the site of a North Korean submarine base and where the North has tested a submarine-launched ballistic missile it is developing.
Impoverished North Korea and the rich, democratic South are technically still at war because their 1950-53 conflict ended in a truce, not a peace treaty.
"North Korea is just trying to gain more attention and gain more leverage," said tourist Huang Xiaojie.
Asked if he believed international media reports, he said no, because "international media often lies and reports negative news about North Korea". »