MELBOURNE, Australia ― North Korea’s nuclear program and China’s continued assertiveness in the South China Sea are expected to dominate a key Asian security conference in Singapore that will be attended by U.S. Defense Secretary Jim Mattis.

Speaking to media while on his way to the annual Shangri-La Dialogue being held in Singapore this weekend, Mattis reiterated that the U.S. will continue to confront China’s militarization of the strategic body of water.which will see defense ministers, military leaders and security professionals gather to discuss regional security matters.

The event will see defense ministers, military leaders and security professionals gather to discuss regional security matters.

Organized by the International Institute of Strategic Studies–Asia, the key topics that will be discussed at the dialogue’s plenary sessions include U.S. leadership and the challenges of Indo-Pacific security, as well as deescalating the North Korean crisis. Other plenary sessions include one on shaping Asia’s evolving security order.

This year’s dialogue will also see Indian Prime Minister Narendra Modi deliver the keynote address June 1, the first time an Indian prime minister has done so since the inaugural Shangri-La Dialogue was held in 2002.

In addition to regional defense ministers, the defense ministers of France, the United Kingdom, Canada and Germany will also be present at this year’s event.

Despite not being explicitly on the agenda, China’s continued militarization of the South China Sea ― where six regional countries are currently party to some or all of the island features in the potentially resource-rich waters ― will almost certainly be discussed. This comes as the U.S. mounted yet another freedom of navigation operation, or FONOP, near two Chinese-held islands over the previous weekend.

The latest FONOP involved two U.S. Navy ships, including the guided-missile cruiser Antietam, sailing within 12 nautical miles of several islands in the Paracels group. This is significant, as it is the first time a known South China Sea FONOP was conducted with two ships, and the first time it has involved a cruiser.

According to Reuters, the ships also carried out maneuvering operations, as opposed to sailing directly across the waters near the islands.

The move has drawn condemnation from China, which has itself landed bombers on an airfield it built on one of the islands it occupies in the Paracels. The country has also reclaimed islands in the disputed Spratly group and built military facilities including airfields, harbors and installing weapons on them.

However, Mattis, who will first stop in Hawaii to oversee a change of command at U.S. Pacific Command, noted that the U.S. vessels were operating in international waters and that “a lot of nations want to see freedom of navigation.”

“There is only one country that seems to take active steps to rebuff them or state their resentment” about the FONOPs, he said, in a likely reference to China.