The booster capability of a new intercontinental ballistic rocket engine could give North Korea the power to target the U.S. with nuclear strikes.

Tensions on the Korean peninsula flared again Monday as South Korea fired warning shots at a North Korean patrol boat.

North Korea launched a long-range rocket on Sunday carrying what it has said is a satellite, South Korea said, in defiance of United Nations sanctions.

North Korean news agency KCNA reported that the country’s leader, Kim Jong Un “made the final decision on January 3rd to go ahead with the hydrogen test.”