In a background briefing with foreign reporters Tuesday, a government official said it appears North Korea has succeeded in miniaturizing a warhead enough to be mounted onto a Rodong missile.
The official -- who remains unnamed as per South Korean government protocol -- says this ballistic missile can deliver a one ton (907 kg) warhead a distance of 2,000 km (1243 miles), putting U.S. military bases in South Korea and Japan within range.
The official said: "We believe they have the ability to mount a nuclear warhead on a Rodong. Whether they will fire it like that is a political decision."
However, the official added they have no evidence to prove this capability, an assessment backed up by the United States.
"We know that they've said they have that capability and we have to take them at their word," Pentagon Spokesman Captain Jeff Davis told reporters Tuesday. "But we have not seen them demonstrate it."
Nuclear plans progressing
Kim Jong Un claimed last month his country had successfully miniaturized a nuclear weapon, as state run media published photos of him next to what it said was the miniaturized warhead.
The briefing came as Washington D.C.-based monitoring project 38 North said that it had logged "suspicious activity
" at the North's Yongbyon nuclear facility.
Pyongyang carried out its fourth nuclear test
on January 6th and has insisted its nuclear program will continue despite further U.N. sanctions passed against the country last month.
The South Korean government official said the focus now should be on implementing these sanctions, adding there may be a level of chaos in the country when the cash starts to dry up but "at this point the leadership of Kim Jong Un is seemingly unshakeable."
Meanwhile, Seoul says recent GPS disruptions carried out by the North ended Tuesday afternoon.
The Ministry of Science, ICT and Future Planning says they traced the jamming to five different areas in North Korea originating on March 31. The ministry says 962 airplanes, 692 ships and 1,785 communication network base stations were affected but no damage reported.
North Korea has not responded to the South's accusation.