U.S. President Barack Obama says that North Korea's artillery attack this week is "one more provocative incident in a series seen over the last several months."

In an interview with Barbara Walters that aired on ABC Friday evening, Obama said the U.S. wants to make sure all the parties in the region recognize that this is a serious and ongoing threat that has to be dealt with.

He said South Korea is a U.S. ally and has been since the Korean War and therefore, Washington strongly affirms its commitment to defend South Korea as part of that alliance.

Obama further stated that the U.S. has united the world to pressure North Korea.

But, he said, he would not speculate on the possibility of military action yet.

The U.S president also urged China to pressure North Korea to follow international rules, calling Bejing one of the few countries that has influence on the communist country.