President Barack Obama urged North Korea to end its "belligerent approach" on Thursday, as a US military intelligence assessment suggested Pyongyang could place a nuclear warhead on a missile.
The dire warning from Washington about the North's nuclear capabilities, revealed by a US lawmaker, came as all eyes were on Pyongyang, which was widely expected to soon launch a missile and trigger a new cycle of tension.
Group of Eight foreign ministers meeting in London drove home the message, condemning "in the strongest possible terms" the North's nuclear activities and threats to the region, which have escalated in recent days.
The North's December rocket launch and February nuclear test, along with UN sanctions imposed for each, are at the core of the current crisis that has seen Pyongyang threaten nuclear strikes against the United States and its allies.
Speaking at the White House, Obama said "nobody wants to see a conflict" with the North, but emphasized that the United States was ready to take "all necessary steps to protect its people" and defend its allies in the region.
"We both agree that now is the time for North Korea to end the kind of belligerent approach that they've been taking," Obama said, appearing by the side of UN Secretary General Ban Ki-moon after talks in the Oval Office.
"It's important for North Korea, like every other country in the world, to observe basic rules and norms."
Ban praised Washington's "measured response" to Pyongyang's threats and called on China to use its influence with its wayward ally.
In Washington, US congressman Doug Lamborn, reading from an unclassified portion of a Defense Intelligence Agency report, said Pyongyang could be capable of launching a nuclear warhead, albeit an unpredictable one.
"DIA assesses with moderate confidence the North currently has nuclear weapons capable of delivery by ballistic missiles," said the report, according to Lamborn. "However, the reliability will be low."
US intelligence agencies declined to comment but issued no statement rebutting the lawmaker's portrayal of the findings.
Foreign spy services and arms experts have struggled to track North Korea's progress in its bid to miniaturize a nuclear device that could be fixed on a ballistic missile.
Ban told CNN there was no independent confirmation of the DIA assessment.
Intelligence officials in Seoul say the North has two mid-range missiles ready for imminent launch from its east coast, and South Korea and Japan remained on heightened alert for any test.
But the North's state media focused its attention on Thursday's first anniversary of new leader Kim Jong-Un becoming head of the ruling Worker's Party and next Monday's birthday celebrations for late founder Kim Il-Sung.
"History has never seen any socialist leader like him," the official party mouthpiece Rodong Sinmun said in praise of Kim Jong-Un, calling him the "No. 1 man of conviction and will."
In apparent reference to its missiles, North Korea said its units were on standby for a launch.
If fired, they would turn enemy strongholds into "a sea of fire," the Committee for the Peaceful Reunification of Korea said via state media.
Although Pyongyang has not announced any launch, many observers believe it will take place during the build-up to the April 15 birthday anniversary.
The missile launch could coincide with some high-profile visits to South Korea, with US Secretary of State John Kerry due in Seoul on Friday. NATO chief Anders Fogh Rasmussen held talks Thursday with Foreign Minister Yun Byung-Se.
Yonhap news agency quoted military sources as saying the North was moving multiple missiles around in an apparent bid to confuse outside intelligence gatherers about its intentions.
The North last week told foreign diplomats in Pyongyang they had until April 10 to consider evacuation, and warned foreigners in South Korea to get out ahead of a possible "thermo-nuclear" war.
The European Union said the seven EU countries with embassies in North Korea saw no need to leave, adding it saw no risk to EU citizens in the South.
Despite the reassurances, there is still growing global concern that sky-high tensions might trigger an incident that could swiftly escalate.
Russian Foreign Minister Sergei Lavrov warned against escalating the crisis, and stressed that Moscow and Washington were cooperating closely.
"On North Korea we have no differences with the United States," Lavrov said after meeting Kerry on the sidelines of the G8 meeting.
The mid-range missiles mobilized by the North are reported to be untested Musudan models with an estimated range of up to 2,485 miles.
That would cover any target in South Korea and Japan, and possibly even US military bases on the Pacific island of Guam.
© AFP 2013