"We have done wishful thinking that North Korea would collapse, and this has shaped our negotiations with them", said Chung-in Moon, distinguished professor emeritus at Yonsei University and former South Korean ambassador for global security affairs.
North Korea has successfully tested a new, high-powered rocket engine, state media said on Tuesday, a move experts say will bolster its already burgeoning weapons programme.
North Korea's leader, Kim Jong Un, ordered preparations for the launch of a satellite "as soon as possible" on the basis of the successful test, its state media reported. The test explosion, the most powerful to date, was conducted on the 68th anniversary of the founding of North Korea's government.
The flyby comes only a week after a pair of B-1B Lancers flew over South Korea days after the North conducted its fifth nuclear test.
North Korea doesn't respond well to shows of power. In the February test, the Kwangmyongsong-4 rocket was assessed to have had 120 tons of thrust using four engines in the first rocket stage. More such cases may follow if the USA or South Korea have firm evidence. "For many years we have been talking about the development of North Korea's nuclear weapons and missiles, and now we may be reaching a stage where we have to worry about the deployment of nuclear-tipped missiles", Yun said.
Last week, USFK Commander General Vincent K. Brooks said, "North Korea's nuclear test is a risky escalation and poses an unacceptable threat".
Officials say North Korea isn't the main motivator for the exercise.
"Some factions in Seoul have renewed calls for a nuclear force in South Korea - which now does not have nuclear weapons", Elise says.
It hasn't demonstrated that ability but some experts say it is likely about two or three years away from showing it can threaten the USA homeland with missiles.
Strengthened sanctions on Pyongyang haven't discouraged Kim Jong Un from building up a nuclear program.
Obama strongly condemned the North's September 9 nuclear test, issuing a rare statement of his own vowing never to accept the North as a nuclear state and pledging to "significant" new sanctions on the communist nation.
High-ranking Chinese financial officials said they have frozen the assets of Ma as well as those of her business associates and relatives, who are believed to have also been offering financial support to North Korea.
Pyongyang tests rocket engine; Seoul says move meant to show progress in being able to hit US.
United Nations diplomats say the two countries have started discussions on a possible United Nations sanctions resolution in response to the nuclear test earlier this month, but Beijing has not said directly whether it will support tougher steps against North Korea.
"It's one and the same", said Jeffrey Lewis, an adjunct professor at the Middlebury Institute, adding that a rocket engine of that size would represent an upgrade to Iran's current capabilities.
The prosecutors said there is enough evidence to pin Ma and her company for aiding North Korea's nuclear program and helping Kim evade United Nations sanctions.
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