South Korea's spy agency does not believe that North Korea has secured the crucial re-entry technology that can allow a warhead to re-enter the Earth's atmosphere after flying through space, reported Yonhap news agency.
Yi Wan Young, who is also a member of parliament's intelligence committee, told reporters during a televised briefing that the National Intelligence Agency also had not detected any unusual activity at the North's nuclear test site.
A re-entry vehicle protects a ballistic missile's warhead through the course of its flight, including the re-entry stage. Without proper protection, a missile's warhead will burn up from the heat and pressure.
North Korea on July 4 test fired a missile that some experts believe could have the range to reach Alaska, and parts of the US West Coast. A day after the launch, North Korea said the missile, Hwasong-14, is capable of carrying a "large, heavy nuclear warhead" that can survive re-entry into the Earth's atmosphere.
Moscow claimed the Hwasong-14 was not an intercontinental ballistic missile (ICBM) but a medium-range missile.
In May 2017, Pyongyang released images of the Earth taken from a camera mounted on a launched missile to show that it has mastered the technology for atmospheric re-entry. The US and its allies have said more analysis is required to verify whether the North had achieved a breakthrough in re-entry technology.
Experts have said that mastering the re-entry technology is a major challenge Pyongyang must overcome if it wants to pose a real threat to the continental US.
The US aims to put to a vote within weeks a United Nations Security Council resolution to impose stronger sanctions on North Korea over its long-range ballistic missile test, said several senior UN diplomats.
The US gave China a draft resolution to impose stronger sanctions on Pyongyang after the 15-member Security Council met on Wednesday to discuss the ICBM launch, diplomats told Reuters.
China's UN Ambassador Liu Jieyi told Reuters on Monday that it was important to ensure that any action the Security Council might take should be conducive to achieving the goal of a denuclearised, peaceful and stable Korean peninsula.
"We really must think very carefully about what is the best approach in the Security Council because a resolution, sanctions, are themselves not an objective," he said.
When asked if the council could act within weeks, Liu said it would depend on how members "see the way forward in terms of council action, in terms of how that is put into the wider context of ... improving the situation, preventing further tests, ensuring Security Council resolutions will be abided by."
Traditionally, the US and China have negotiated new sanctions on North Korea before formally involving other council members.
Diplomats said the United States would informally keep Britain and France in the loop, while China was likely talking to Russia. The US, China, Russia, Britain and France are the Security Council's permanent veto-wielding powers. The United States could also face a battle to persuade Russia that council action against North Korea is needed.