Defense Minister Shin Won-sik on Thursday downplayed concerns over the US potentially shifting to a softer stance on North Korea's nuclear program amid the possibility that former US President Donald Trump could win the November presidential election.

Shin made the remark as a ruling party lawmaker raised concerns that calls for seeking a freeze of the North's nuclear program, instead of its denuclearization, could gain momentum in the US as Pyongyang pushes to advance its intercontinental ballistic missiles.

"If the U.S. falls under the influence of North Korea's blackmail and abandons its duty to its ally, it would have to give up its global leadership," Shin said during a National Assembly session.

Concerns have also grown over Trump's possible policy shift over North Korea's denuclearization if he is elected, with some experts suggesting he could allow the North keep its nuclear program under certain conditions.

Shin also dismissed the possibility of the alliance becoming weaker even if North Korea deploys an intercontinental ballistic missile, which would put the US mainland within range, citing the "extended deterrence" system between the allies.

Extended deterrence refers to the US commitment to mobilizing the full-range of its military capabilities to defend an ally.

Shin also warned against possible provocative acts by North Korea near the Northern Limit Line (NLL), the de facto inter-Korean sea border, after the North's leader Kim Jong-un called the boundary a "ghost line" without legal grounds last week.

"Our military has defended the NLL over the past 70 years as the de facto maritime boundary," he said. "If Kim Jong-un makes the wrong choice, (it) will be a big disaster."

The North has recently ratcheted up tensions by staging a spate of weapons demonstrations this year.

It fired multiple cruise missiles off its east coast last week in its fifth such missile launch this year.