"He didn't say if that happens, the president sends an emissary to the Blue House and we will consult and ask permission of South Koreans as to whether we can adequately defend America and its interests," he said, referring to South Korea's presidential office Cheong Wa Dae. "He didn't say that because it's not true."

Gallucci, who now heads the US-Korea Institute at the Johns Hopkins School of Advanced International Studies, noted it would have been useful for Moon and US President Donald Trump to discuss the issue during the summit last week if it was so important to Seoul.

He added the caveat that he does not think Washington would take military action without communicating its decision with Seoul, but the bilateral alliance does not mean the US will not defend itself if necessary.

"It means we will take action taking full account of our obligations to our allies South Korea and Japan," he said.

Gallucci made the remarks shortly after he took part in a separate public discussion with South Korea's ruling Democratic Party leader Choo Mi-ae.

Choo, who is currently on a visit to Washington, had told the forum that South Korea would not accept war on the Korean Peninsula without its consent under any circumstances.

"I find that a reach, which is my way of saying it's not likely at all," Gallucci said.

The 1994 agreement he negotiated called for North Korea to freeze and ultimately dismantle its nuclear program in exchange for political and economic concessions. It later fell through with the outbreak of the second nuclear crisis in 2012 after the North was found to have been running a clandestine program to enrich uranium for nuclear weapons. (Yonhap)