Mattis: 'Bumpy road' to summit

US Defense Secretary Jim Mattis said the DPRK will receive relief only after it takes clear and irreversible steps to end its nuclear program, adding it would be a bumpy road to a summit between leaders of the United States and the Democratic People's Republic of Korea.

Mattis made the remarks on Sunday at the 17th Asia Security Summit, commonly known as the Shangri-La Dialogue, which opened in Singapore on Friday.

"We can anticipate, at best, a bumpy road to the negotiations," Mattis said. "In this moment we are steadfastly committed to strengthening even further our defense cooperation as the best means for preserving the peace."