Delivering the first State of the Union address of his second term, U.S. President Barack Obama said Tuesday that his administration will strengthen missile defense against North Korean threats.

Citing North Korea's nuclear test earlier this week, Obama said such a provocative act will only deepen the communist nation's isolation.

 "America will continue to lead the effort to prevent the spread of the world's most dangerous weapons," he said in a speech at Capitol Hill. "The regime in North Korea must know that they will only achieve security and prosperity by meeting their international obligations."

He added, "Provocations of the sort we saw last night will only isolate them further, as we stand by our allies, strengthen our own missile defense, and lead the world in taking firm action in response to these threats."

Obama briefly mentioned North Korea in his speech which focused on his domestic agenda of creating jobs and boosting the economy.

Obama did not touch on Korea issues in his State of the Union address last year. (Yonhap News)