South Korea's Unification Minister Cho Myoung-gyon told lawmakers on Tuesday that estimates on the size of the North’s nuclear arsenal ranged from 20 bombs to as many as 60.
Cho said the information came from the intelligence authorities, Presstv Reported.
However, the minister said this did not mean South Korea would accept the North as a nuclear state. He also suggested that Seoul's diplomatic efforts to halt the North's nuclear program continue.
According to Seoul’s government reports, the North is believed to have produced 50 kilograms of weaponry plutonium, enough for at least eight nuclear bombs.
It is the first time a senior South Korean official has publicly spoken about the size of the North's secretive haul of weapons.
Peace treaty no bargaining chip for denuclearization: North Korea
In a commentary, North Korea's official Korean Central News Agency (KCNA) warned Washington on Tuesday that it cannot use a declaration to end the Korean War as a bargaining chip. However, it suggested the lifting of sanctions could progress talks.
"The end of war... is not just a gift from a man to another at all. Furthermore, it can never be a bargaining chip for getting the DPRK denuclearised," it said, using the North's official name.
The North has for decades demanded that the US formally declare the end of the 1950-53 conflict that was halted only with an armistice.
The North's official news agency said its government has taken significant measures to end hostile relations with its southern neighbor. But it maintained that the US was "trying to subdue" it through sanctions.
KCNA said that Pyongyang was willing to take "such... steps as eternal dismantlement" of its nuclear complex "if the US takes a corresponding measure"
At a summit with the South's President Moon Jae-in last month, the North's leader Kim Jong-un offered to shut down its main Yongbyon nuclear complex if Washington takes "corresponding measures".
US President Donald Trump met with Kim in June in what was the first-ever summit between the two countries, praising the North Korean leader for taking positive steps toward denuclearization.
Observers describe as mixed signals between North Korea and the US with some analysts doubting true changes in the two countries’ positions beyond rhetoric.
Talks have been marred by US accusations that Pyongyang is violating UN sanctions and that the country remains “a significant threat.”
The North has responded by saying that Washington has betrayed the spirit of the summit by making unilateral demands while maintaining sanctions in place, effectively hindering inter-Korean relations.
Pyongyang has firmly defended its military program as a deterrent against the hostile policies of the US and its regional allies, including South Korea and Japan. Thousands of US soldiers are stationed in South Korea and Japan.