Obama condemns North Korea after latest missile launches
Barack Obama has said the United States will work with allies to toughen sanctions on North Korea after further ballistic missile launches on Monday.
But the US President added that there is room for dialogue if North Korea changes direction.
President Obama's comments come after a meeting with President Park Geun-hye of South Korea.
The two leaders are attending a meeting of the Association of Southeast Asian Nations in Laos. He said the two leaders want peace and security for all peoples.
President Obama said the latest North Korea launches are provocative and that North Korea needs to know that such actions will increase its isolation in the world.
Mr Park said a nuclear test and continued missile launches are fundamentally threatening the security of the Korean Peninsula.
"We are going to work diligently together with the most recent UN sanctions," President Obama told reporters after meeting with Mr Park.
"We are going to work together to make sure we're closing loopholes and make them even more effective."
North Korea fired three ballistic missiles off its east coast on Monday. The launch was widely viewed as a show of force timed to get the attention of world leaders visiting the region for a series of summits.
The UN Security Council in late August strongly condemned four North Korean ballistic missile launches in July and August. It called them "grave violations" of a ban on all ballistic missile activity.
Despite the heavy sanctions, North Korea says the programmes are justified because of the threat posed by the US and South Korea.
Both leaders suggested they would continue to push China, North Korea's only ally in the region, to use its influence to intervene.
"President Park and I agreed that the entire international community needs to implement these sanctions fully and hold North Korea accountable," President Obama said.
He added that the US had not closed off the possibility for dialogue with North Korea, if it were to change course.
"If it is willing to recognise its international obligations and enforce the denuclearisation of the Korean Peninsula, the opportunities for us to dialogue with them are there," President Obama said.
"We do not have any interest in an offensive approach to North Korea."