WASHINGTON — President Obama said that the United States is re-positioning its missile defense system in the wake of provocative actions from North Korea, but he acknowledged that the isolated Northeast Asian nation poses a “massive challenge” for the United States and its allies.

“Our first priority is to protect the American people and our allies, [South] Korea and Japan,” Obama said in an interview with “CBS This Morning” broadcast Tuesday. “One of the things we have been doing is spending a lot more time positioning our missile defense system so that even as we try to resolve the underlying problem of nuclear development inside of North Korea, we’re also setting up a shield that can at least block the relatively low level threats they are posing right now.”

North Korea is reportedly readying a test of an intermediate-range ballistic missile, according to South Korea’s Yonhap news agency. That report comes after Pyongyang conducted a series of tests, including a reported nuclear bomb test in January and a long-range rocket in February. The nuclear test drew international condemnations and fresh U.N. economic sanctions.

Last month, the United States and South Korea began talks over the potential deployment of Terminal High Altitude Area Defense on the peninsula.

Obama told interviewer Charlie Rose that North Korean dictator Kim Jong Un is “personally irresponsible” and that “we don’t want them to get close, but it’s not something that lends itself to an easy solution.”

The president added that “we could obviously destroy North Korea with our arsenal, but aside from the humanitarian costs of that, they are right next door to our vital ally,” South Korea.

The Obama administration has sought to convince China to exert greater pressure on Pyongyang, and Beijing supported the U.N. sanctions.

Of China, Obama said Beijing tends to view regional issues and disputes as a “zero-sum game” and that the Asian power bullies its neighbors in the South China Sea.

“Rather than operate under international norms and rules, their attitude is, ‘We’re the biggest kids around here, and we will push aside the Philippines or the Vietnamese,’ ” Obama said. “That doesn’t mean we are trying to act against China. We just want them to be partners with us. Where they break out of international rules and norms, we will hold them to account.”