North Korea is making more threats, just one day after President Obama met with South Korea's president in Washington.
On Wednesday, the communist regime vowed "one-thousand-fold retaliation with a "merciless military strike" if the U.S. infringes on its sovereignty.
The threats from the north come amid other signs of military escalation.
Japanese and South Korean news reports that North Korea is preparing a new site for test-firing a long-range missile.
On Capitol Hill Tuesday, Deputy Defense Secretary William Lynn warned North Korean missiles could hit the U.S. in three years if the north continues its weapons program.
"We think it ultimately could, if taken to its conclusion, it could present a threat to the homeland," he said.
President Obama met with South Korea's president at the White House Tuesday. The two agreed to build a strategic alliance to persuade North Korea to dismantle its nuclear weapons.
Obama used his strongest language yet to condemn the north's nuclear program.
"I don't think there's any question that would be a destabilizing situation that would be a profound threat not only to United States' security, but to world security," the president said.
The deteriorating situation could be considered to be the president's first major international test. CBN News Chief International Correspondent Gary Lane gave his analysis on CBN News' Newswatch program Tuesday.
"It's hard to imagine anything worse than a nation that has detonated two nuclear devices threatening nuclear war," he explained. "The bad news is this is causing worries and concern in an area of the world that comprises about one-sixth of the world's economy."
For its part, the north claims its nuclear bombs are a deterrent against the U.S. and accuses Washington of plotting with Seoul to topple North Korea.