Moon Chung-in, a professor at Yonsei University, also said that this means that there is still time for the international community to resolve the North's missile and nuclear stalemate through peaceful means.

"My personal view is that the US State Department and Secretary of State Tillerson both came to a conclusion too easily (about the North's missile capability)," he said at a seminar held in central Seoul.

"They called it an ICBM and said that the North has secured ICBM capability but the US appears to have overestimated its capacity," he added.

Early on Tuesday, the North fired a ballistic missile toward the East Sea. It was initially seen as an intermediate missile but Pyongyang later said in a televised announcement that it successfully test-fired an ICBM, named Hwasong-14.

US Secretary of State Rex Tillerson confirmed that North Korea's latest missile launch was an ICBM, indicating that Pyongyang has moved much closer to perfecting capabilities to deliver a nuclear warhead on such missiles capable of hitting the continental US.

In a UN Security Council meeting on Wednesday (local time), US Ambassador Nikki Hailey said that military force could be used against North Korea if necessary and warned that its continued provocations are "quickly closing off" chances of a diplomatic solution.

"There are no data about whether the missile can withstand the heat when making re-entry to the atmosphere, whether it is possible to control its deceleration and if an actual nuclear warhead can be loaded onto its tip," Moon said.

"To secure stability in missiles, they have to be tested about 15 times but there have not been many tests. From a technological point of view, it is hard to say that the North has secured an ICBM capability," he added. "This means we still have time."

Moon said that he recently talked to Theodore Postol, a professor at the Massachusetts Institute of Technology, through emails in which he asked whether the missile that the North tested on Tuesday is a "precursor" or "prototype" from which it can be mass produced. The professor answered that the former was right, meaning that it is in the initial stage of developing an ICBM, he added.

"If an ICBM can be mass produced, it would be hard to seek negotiations but is it still possible to seek talks?" he said. "A majority of experts in Washington say that there is still room for talks... The mainstream opinion is that there is room for talks so let's solve this problem peacefully." (Yonhap)