The remarks came hours after President Moon Jae-in and U.S. President Donald Trump held their second telephone conversation in just two days to discuss ways to rein in North Korea's evolving missile technology.
"The issue of a naval blockade was never mentioned in the phone call with President Trump," the official told reporters, speaking on condition of anonymity.
The possibility of a naval blockade surfaced immediately after North Korea launched what is believed to be an intercontinental ballistic missile (ICBM) in the small hours of Wednesday, ending its 75-day hiatus in provocations.
Many experts have said the idea is the only possible option available, as Seoul and Washington have long been maintaining what they called "the strongest" sanctions and pressure against North Korea under bilateral and international efforts.
The Cheong Wa Dae official noted the countries continue to move toward maximum sanctions and pressure but said there are many other options left, such as a complete cutoff of oil supplies to the communist state, as suggested by Trump.
"I may not discuss every detail of the call between the two leaders, but I can confirm that there were no suggestions or discussions about military steps or a naval blockade," he said.
While speaking in a parliamentary session later, Defense Minister Song Young-moo noted Seoul "cannot help but mull" a naval blockade should there be such a request. He also went on to say that if a proposal is made, the government will "actively and positively" consider it.
The Cheong Wa Dae official quickly dismissed Song's remarks as a personal view.
"The issue has not been discussed, reviewed or reported at the government or the National Security Council level," the presidential aide said.
The official also insisted the North's latest missile provocation may not warrant military action despite Pyongyang's earlier claim that the launch was successful and that it marked the completion of building what it called a "state nuclear force."
"We and the United States do not accept North Korea's declaration of being a nuclear state itself," the official said, adding that the president too has stressed the need to first verify the North's claimed success in its latest missile test.
In his second telephone call with Trump, the South Korean leader was quoted as saying the North's claim to have completed the development of an ICBM has not been confirmed. Source from the Yonhap.