South Korea’s Defense ministry said on Friday it doubted North Korea had the ability to launch a nuclear-armed ballistic missile as reported earlier by the US military spy agency.

South Korea's Defense ministry said on Friday it doubted North Korea had the ability to launch a nuclear-armed ballistic missile as reported earlier by the US military spy agency.

North Korea has conducted three nuclear tests, but it is still doubtful that North Korea has made a small, light warhead that can be mounted on a missile," AFP quoted Ministry Spokesman Kim Min-Seok as saying before reporters.

However, the North was "getting to that stage" where it could miniaturize a warhead for missile deployment.

US Defense Intelligence Agency (DIA) had stated that Pyongyang could be capable of launching a nuclear warhead.

In parallel, the United States slammed North Korea's “belligerence” on Thursday and pressed China to rein in its ally.

A senior official traveling with US Secretary of State John Kerry to Seoul, where he was due on Friday, again pressed China to encourage its ally to stop its nuclear activities and threats to the region.

For his part, US President Barack Obama said "nobody wants to see a conflict," but emphasized that the United States was ready to take "all necessary steps to protect its people and defend its allies in the region.”

“We both agree that now is the time for North Korea to end the kind of belligerent approach that they've been taking," Obama said after talks in the Oval Office with UN Secretary General Ban Ki-moon.

"It's important for North Korea, like every other country in the world, to observe basic rules and norms."

The top US official traveling with Kerry, who will also visit Beijing and Tokyo during his trip to Asia, said China had a key role to play in the crisis.

"China has a huge stake in stability, and the continued North Korean pursuit of a nuclear-armed missile capability is the enemy of stability," AFP quoted the official as saying.