A South Korean presidential adviser says a possible North Korean rocket launch would be "catastrophic" for diplomacy on the North's nuclear program.

U.S.-based websites recently released satellite photographs indicating that North Korea has restored structures at its long-range rocket launch facility that it dismantled last year.

The satellite imageries were released days after the second U.S.-North Korea summit in Vietnam ended without any agreement.

Moon Chung-in, a special adviser to President Moon Jae-in, told a panel discussion Tuesday that North Korea using a rocket launch as leverage in negotiations would be a "bad move."

He says both North Korea and the U.S. must restrain themselves to keep diplomacy alive.

Moon says the Hanoi summit showed how "difficult" and "painful" to achieve denuclearization on the Korean Peninsula.