Former U.S. Defense Secretary Robert Gates said Wednesday he believes North Korea will eventually succeed in developing submarine-launched ballistic missiles.

"They're working on submarine-launched ballistic missiles and that capability. And they have the successive failures, but eventually they're going to get it right and that's going to be a very dangerous situation, all of which is diagnosis without a prescription for how you solve the problem," Gates said during a Council on Foreign Relations seminar.

The North is believed to have conducted at least three SLBM tests in May, November and December last year, but experts and officials say that the communist nation is still many years away from mastering SLBM capabilities.

Gates said North Korean leader Kim Jong-un is dangerous and has a record of belligerence, claiming that the young leader was behind the North's sinking of the South Korean warship Cheonan and the shelling of the South Korean island of Yeonpyeong in 2010 "to prove his mettle to the North Korean leadership that he was tough enough to take on the job."

"I think this is a very dangerous situation. This guy is developing a road-mobile ICBM. He wants to develop a hydrogen weapon -- my guess is he doesn't have one yet. And so, it's a very difficult situation," he said. (Yonhap)