South Korea says it believes that North Korea has up to 60 atomic bombs – but refuses to accept that it is a nuclear state.
Estimates of the size of the nuclear arsenal of the isolated nation range from 20 bombs to 60 bombs, said Minister for Reunification Cho Myoung-gyon in parliament.
This is the first time that a high-ranking Seoul official has spoken publicly about the size of the North's secret weapons movement.
Mr. Cho said the information came from the intelligence services.
However, he said that this did not mean that South Korea would accept North Korea as a nuclear state, suggesting that Seoul's diplomatic efforts to halt the North's nuclear program would continue.
According to South Korean government reports, the north is said to have produced 50 kg (110 lbs) of weapons-grade plutonium, enough for at least eight nuclear bombs.
South Korea's main spy agency, the National Intelligence Service, did not comment immediately.
As the denuclearization talks between the US and North Korea continue to falter, Pyongyang has warned Washington that it can not use any explanation to end the Korean War as a bargaining chip.
However, it was suggested that the lifting of the sanctions could advance the discussions.
The two Koreas are technically still at war, because although a ceasefire was signed in 1953, a peace treaty has never been concluded.
In April, the leaders of North and South Korea met in the demilitarized zone between the two states and agreed to sign a treaty by the end of the year.
The official news agency of the North said its government under the leadership of dictator Kim Jong Un has taken significant steps to end hostile relations with its southern neighbor.
But it claimed that the US was "trying to tame it with sanctions" – an unappealing demand on Washington to lift its sanctions if it wanted to make progress in its stalled nuclear negotiations.
An editorial in a state-owned North Korean newspaper said a statement replacing the 65-year-old ceasefire to literally end the war is "not just a gift from one man to another."
"It can never be a negotiating crepe to make the Democratic People's Republic of Korea denuclear," he added.
US Secretary of State Mike Pompeo is expected to travel to North Korea soon to resume negotiations and set the course for a second summit between Donald Trump and Kim.