President Obama in a Wednesday interview with ABC urged North Korea to pursue "confidence-building measures" such as ceasing tests of nuclear devices and missiles in order to improve the regional security climate, Voice of America reported.
The North has lashed out after being hit with another round of U.N. Security Council sanctions for carrying out a nuclear test on Feb. 12. It has threatened pre-emptive nuclear strikes on South Korea and the United States and has said it would no longer abide by the Korean War armistice.
Other nations would respond in kind with trust-enforcing actions if they see Pyongyang move to obey international norms, the president said.
Obama said he sees "promising" indicators from China, which has traditionally acted to shield North Korea from strong international punishments for its provocations, Agence France-Presse reported. "You're starting to see them recalculate and say, 'You know what? This is starting to get out of hand," he said without providing specific instances of how the Chinese government is cooperating more on North Korea.
China joined with the 14 other members of the Security Council last week in unanimously approving new sanctions that target Pyongyang's ability to obtain foreign currency and import materials for its WMD programs.
As Beijing comes around, "we may slowly be in a position where we're able to force a recalculation on the part of North Koreans," according to Obama.
Obama said he believes the North lacks the military capability to carry out its nuclear strike threat against the United States, CNN reported. "They probably can't, but we don't like the margin of error."
Meanwhile, international scientists have been unable to figure out what type of fissile material the Stalinist state used to power the nuclear device it detonated underground last month at Punggye-ri.
North Korea used plutonium in its two previous atomic blasts in 2006 and 2009. Ahead of the most recent trial, experts speculated the North could employ weapon-grade uranium, which it is suspected of generating under a uranium enrichment program that the country claims is for atomic energy purposes.
An unidentified U.S. official told CNN the National Intelligence Director's Office has not changed its original assessment that the Feb. 12 detonation had an explosive force of several kilotons.
"If they used highly enriched uranium, that would be very worrisome because it would suggest they have a larger supply of this material that would allow them to build a larger number of nuclear weapons," according to Arms Control Association Executive Director Daryl Kimball.
There has been no discovery of any radioactive particles or noble gases connected to the test, and none is expected at this point. If the cavity where the test took place was far enough underground and entirely sealed off from the outside environment, radioactive emissions created from the blast would have a hard time escaping, Kimball said.
Separately, North Korean ruler Kim Jong Un oversaw a live munitions exercise not far from a contested maritime boundary line with the South, Reuters reported on Thursday.
North Korean state media also condemned recent calls by a handful of conservative South Korean lawmakers who want their government to establish a national nuclear weapons program, the Yonhap News Agency reported.