Defense Secretary James Mattis is traveling in East Asia to meet with his counterparts to discuss shared security challenges such as North Korea, terrorism in the region, and maritime disputes, and to reassure them of U.S. commitment.

Mattis began his trip on Monday at the Association of Southeast Asian Nations’ Defense Ministers Meeting-Plus (ADMM-Plus) at the former Clark Air Base in Pampanga, Philippines, on Monday where he gathered with 18 defense ministers.

“Meeting participants recognized the importance of the ADMM-Plus as an inclusive platform for high-level discussions of strategic defense and security matters including North Korea, terrorism and maritime security, as well as to promote practical cooperation and confidence-building among their defense establishments,” Pentagon Chief Spokesperson Dana White said in a statement on Tuesday.

“Secretary Mattis ‎reaffirmed the United States’ commitment to allies and partners across the region, and to a free and open Indo-Pacific, which includes a strong ASEAN that speaks with one voice on regional and global issues,” she said.

The nations present included the ten ASEAN member states: Brunei Darussalam, Cambodia, Indonesia, Lao PDR, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Vietnam; and eight “Plus” countries: Australia, China, India, Japan, New Zealand, South Korea, Russian Federation, and the U.S.

They discussed the need to increase cooperation on countering “violent extremism” and the threat posed by foreign fighters returning to the region from Iraq and Syria.

The Islamic State in Iraq and Syria (ISIS) has unsuccessfully sought to establish a presence in the southern Philippines as they began losing their physical bases in Iraq and Syria. Mattis proposed a “tabletop exercise” to exchange lessons learned from the counter-ISIS campaign and a workshop on regional terrorist threats.

Mattis thanked ASEAN members for U.S.-ASEAN military cooperation and encouraged “increased operational cooperation” on maritime security challenges. That included increasing the “scope and complexity” of military exercises as well as intelligence and information sharing, according to the statement.

While at ASEAN, Mattis took part in the ninth trilateral defense ministerial with his Japanese and South Korean counterparts. They issued a statement that strongly condemned North Korea’s ongoing provocative actions, according to a Pentagon statement.

They called on North Korea to abandon its illegal nuclear and ballistic missile program, stop testing ballistic missiles and nuclear weapons, and to abide by international obligations and commitments.

The ministers pledged to “actively cooperate to support diplomatic-led efforts to resolve the North Korean nuclear issue through maximum pressure,” they said, according to a statement by the ministers.

They also committed to continuing efforts to “backstop the international community’s efforts,” it added.

They also “lauded efforts” to increase information sharing on North Korea, enhance “response capabilities” such as joint flyovers with U.S. bomber aircraft, and they committed to continue missile warning and anti-submarine warfare exercises.

“Our security is interconnected and we speak with a single voice in holding DPRK accountable. And America’s commitment to the defense of the Republic of Korea and Japan, two of our most respected allies, remains ironclad because we recognize we are stronger together. Together we remain committed to forging a future-oriented defense relationship based on mutual respect and shared values,” Mattis said at a press conference on Monday.

The group also reportedly discussed the importance of maritime security – a likely reference to China’s growing assertiveness in territorial disputes with other nations in the East and South China Seas.

They reaffirmed they are committed to maintaining a “rules-based order,” another potential message to China, whom the West perceives as seeking to challenge that order.

Mattis held several one-on-one meetings with defense ministers.

Mattis met with Japanese Defense Minister Itsunori Onodera and reaffirmed that the U.S.-Japan alliance is the “cornerstone of peace, prosperity, and freedom in the Asia-Pacific region,” according to a DOD statement.

He reaffirmed the U.S. commitment to defend Japan, including the Senkaku Islands in the East China Sea that China also claims.

Mattis then met with South Korea’s Defense Minister Song Young-moo. Mattis reaffirmed that the U.S.-South Korea alliance is the “linchpin of peace and security in the Asia-Pacific region,” the statement said.

On Tuesday, he met with Vietnamese Defense Minister Ngo Xuan Lich to discuss deepening the bilateral defense relationship, particularly in maritime security.

Mattis also met with Philippine Secretary of National Defense Delfin Lorenzana and “reaffirmed the United States’ ironclad commitment to the U.S.-Philippines Alliance and the importance of strengthening defense capabilities through regular bilateral training and exercises.”

He also met with Philippines President Rodrigo Duterte, reaffirming U.S. resolve to stand by the country in their fight against ISIS and congratulated Philippine forces in defeating ISIS’s attempt to establish a stronghold in Marawi.

On Wednesday, he met with Malaysian Minister of Defense Hishammuddin Tun Hussein, to exchange views on shared security interests, including freedom of navigation and fighting terrorism.

The defense secretary then led the official U.S. delegation to the funeral of Thai King Bhumibol Adulyadej, who died in October 2016.

Mattis arrived in Seoul on Wednesday, to chair the 49th annual Security Consultative Meeting. At the same time, a third aircraft carrier arrived in the Asia Pacific.