Stephen Bosworth also said accusations coming from Pyongyang that U.S. aggressions prompted its nuclear and missile tests were "simply groundless," CNN reported Wednesday.
"Quite to the contrary, we have no intention to invade North Korea or to change its regime through force and we have made this clear ... repeatedly," Bosworth said during his speech Tuesday.
North Korea last month conducted its second underground nuclear test, fired test rockets, and threatened U.S. and South Korean ships near its territorial waters. The weaponry tests drew international criticism.
"North Korea's recent actions to develop a nuclear capacity and an intercontinental ballistic missile capacity will require that we expand our consideration of possible responses, including our force posture and options for extended deterrence," Bosworth said. "However, the North Korean claim to be responding to a threat or a hostile policy by the United States is simply groundless."
The Obama administration has said it wants North Korea to return to stalled negotiations for its denuclearization with the United States, China, South Korea, Japan and Russia.