In a separate statement on Thursday, the South Korean navy said the Korea-based three-axis system that includes Kill Chain, Seoul's pre-emptive strike system, is under review.
The regime also blamed the United States for "creating tension on the eve of war" by taking part in civilian evacuation drills in South Korea.
She cited this week's "unprecedented" joint naval drills between the United States and South Korea that began Monday and ended earlier Friday, involving about 40 vessels including an aircraft carrier, as well as recent B1-B strategic bomber flights over the Korean Peninsula.
During an interview with CNBC, Mr Lee outlined his concerns, stressing that while North Korea has postured and made threats for a long time, the danger is "different this time". The North Korean state-run news agency warned, however, that "reckless military gambling against the DPRK" may result in the "total destruction" of the US.More news: Kenya's election chief fears presidential vote won't be credible
- Kim Jong-un desperately wants relations with the U.S.
In particular, they stressed the need for China and Russian Federation to play a greater role in reining in North Korea and have the regime return to the negotiation table.
Tensions have increased between Pyongyang and Washington since the regime began testing intercontinental ballistic missiles that could hit the USA mainland.
The new Sept 21 sanctions will be the first to target all North Korean nationals and the first that delegates to the Treasury Department the authority to go after any foreign bank doing business with North Korea, including banks in China that prop up or finance the regime.