North Korea has erected a new, taller launch tower at its missile base, possibly in preparation for firing a long-range rocket to mark an important national anniversary in October, South Korea's Yonhap news agency has reported.
The 67-metre tower will be able to accommodate the launch of a longer-range missile than the rocket test-fired in December 2012. That launch was widely considered successful in putting an object into space orbit, the Yonhap report said.
North Korea is banned under United Nations Security Council resolutions from conducting tests that use ballistic missile technology but has defied international warnings and sanctions to pursue missile and nuclear programmes.
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"Our assessment is that the North will use the newly upgraded Tongchang-ri [missile] launch pad to launch a long-range missile larger than Unha-3," Yonhap quoted a South Korean government source as saying.
Unha-3 refers to the long-range rocket fired in 2012 from the base near its west coast.
The launch is likely to come around the 70th anniversary of the founding of the North's ruling Workers' Party on October 10, the source was quoted as saying.
South Korea's defence ministry could not immediately confirm the report but an official said they were seeking to verify it.
North Korea is believed to be developing an intercontinental ballistic missile (ICBM) but is seen as years away from deployment. It is also working to miniaturise a nuclear warhead to mount on a delivery vehicle.
The report about the North's launch tower upgrade came as Pyongyang said it has "no interest at all" in an Iran-like dialogue with the US over giving up its nuclear capabilities.
The country's foreign ministry said in a statement on Tuesday that its nuclear programme was an "essential deterrence" against the "provocative" US foreign policy towards North Korea.
"It is not logical to compare our situation with the Iranian nuclear agreement because we are always subjected to provocative US military hostilities, including massive joint military exercises and a grave nuclear threat," said the statement, which was carried by state media.