US President Barack Obama and South Korean President Park Geun-hye hold a meeting in Vientiane, Laos, September 6, 2016. (AFP photo)
US President Barack Obama has vowed to work with the UN to tighten international sanctions against North Korea, a day after Pyongyang launched another round of ballistic missiles into the sea.
“We are going to work together to make sure we’re closing loopholes and make them even more effective,” Obama told reporters on Tuesday after meeting with South Korean President Park Geun-hye in Laos at a summit of the the Association of Southeast Asian Nations (ASEAN).
Obama said the latest launches of ballistic missiles during the G20 summit in China were provocative and that the country needed to know such actions would increase its isolation in the world.
However, the president added that Washington was still open to dialogue if Pyongyang changes its policy.
“If (North Korea) is willing to recognize its international obligations and enforce the denuclearization of the Korean Peninsula, the opportunities for us to dialogue with them are there,” Obama said. “We do not have any interest in an offensive approach to North Korea.”
Park, meanwhile, said North Korea was “fundamentally threatening the security” of the Korean Peninsula.
On Monday, North Korean leader Kim Jong-un urged the nation’s military to bolster its nuclear capabilities after ordering the launch of three ballistic missiles.
“He stressed the need to continue making miraculous achievements in bolstering up the nuclear force one after another in this historic year," said the North’s official KCNA news agency.
The UN and the West have imposed a raft of sanctions on North Korea, prompting Pyongyang to step up its nuclear activities. 
In January, North Korea said it had successfully detonated a hydrogen bomb, its fourth nuclear test, and vowed to build up its nuclear program as deterrence against potential aggression from the US and its regional allies.
A month later, Pyongyang launched a long-range rocket which it said placed an earth observation satellite into orbit. Washington and Seoul denounced it as a cover for an intercontinental ballistic missile test.
The UN has adopted five rounds of crippling sanctions on the North since it first tested an atomic device in 2006 despite the nation's critical situation, including its worsening famine.