China's pressure over North Korea is 'capital'

China's role is "capital" in deterring North Korea to continue its nuclear program, said Thursday in Tokyo, the U.S. President Barack Obama.

"The participation of China in pushing North Korea into a different direction is paramount," said the U.S. president in a press conference in the Japanese capital, where he began a tour of Asia.

"North Korea commits provocative actions for several decades already.It's the most isolated country in the world," the president said.

"North Koreans are subject to sanctions and international condemnation more than any country in the world," he added.

"By cooperating with Japan, South Korea and China, we can exert more pressure on North Korea for it to move in one direction or another," said the U.S. president.

These statements took place in the context in which Washington, Seoul and Tokyo are afraid that the regime in Pyongyang could do, in a short period of time, its fourth nuclear test.