President Obama on Tuesday condemned North Korea’s latest “provocative” ballistic missile launch and pledged to tighten sanctions against the nation.

{mosads}“These launches are provocative,” Obama told reporters after a meeting with South Korean President Park Geun-hye in Laos. “North Korea needs to know that provocations will only invite more pressure and further deepen its isolation.”

Obama said he would “work diligently together with the most recent [United Nations] sanctions,” adding, “We’re going to work together to make sure that we’re closing loopholes and making them even more effective.”

The president’s comments came one day after North Korea fired three mid-range ballistic missiles near the Sea of Japan, prompting renewed concern among U.S. allies in the region.

The launch was timed to coincide with a summit of leaders representing the Group of 20 industrialized nations, or G20, in China.

Over the past year, Obama has condemned each round of missile launches by Pyongyang, and his administration helped convince China, the country’s only major ally, to sign on to the latest set of international sanctions.

But the president has faced criticism from some national security experts that the sanctions have not succeeded in changing North Korea’s behavior.

Park said that her neighbor’s “continued missile launches are fundamentally threatening the security of both the Korean Peninsula and Northeast Asia.”

Obama said that he’s open to having discussions with the North Korean government, but only if Pyongyang decides to drop its nuclear ambitions.

“If it is willing to recognize its international obligations and the importance of denuclearization in the Korean Peninsula, the opportunities for us to dialogue with them are there,” he said. “We do not have any interest in an offensive approach to North Korea.”