International and regional security concerns will take center stage at the Association of Southeast Asian Nation Summit this week, as leaders will likely apply pressure on China and Russia over ongoing geopolitical conflicts.

US Secretary of State Antony Blinken and Japan's newly elected Prime Minister Shigeru Ishiba both confirmed their trip to Vientiane, Laos, Tuesday. Beijing also confirmed that Chinese Premier Li Qiang will attend the multilateral meetings.

President Yoon Suk Yeol's office on Oct. 3 unveiled Yoon's itinerary during the summit period, as he is poised to attend the South Korea-ASEAN summit, the ASEAN Plus Three summit and the East Asia Summit. Vientiane is the final stop of his weeklong trip to Southeast Asia, following visits to the Philippines and Singapore.

During his trip to Laos, Blinken will "discuss pressing geopolitical issues, including the ongoing crisis in Burma (Myanmar), the importance of upholding international law in the South China Sea and Russia’s aggression against Ukraine," Daniel Kritenbrink, assistant secretary for East Asian and Pacific affairs in the United States, said in a teleconference Tuesday.

Kritenbrink also said China’s support for the Russian defense industrial base "is helping to fuel Russia’s war against Ukraine," urging China to "take responsible steps."

As for the territorial disputes in the South China Sea between China and Southeast Asian countries like Vietnam, the Philippines, Malaysia and Brunei as well as Taiwan, China is responsible for "a number of escalatory and irresponsible steps designed to coerce and pressure many in the South China Sea claimants," Kritenbrink added.

Against this backdrop, Yoon would likely unveil his stance on these security issues during the South Korea-ASEAN summit on Thursday and the East Asia Summit on Friday, a source from South Korea's presidential office said on condition of anonymity. But he would not make security-related remarks at the ASEAN Plus Three, also attended by China's Li and Japan's Ishiba, the source added.

Seoul is also expected to denounce North Korea's nuclear ambitions and discuss repercussions on the Indo-Pacific region.

Before Yoon's arrival in Vientiane on Wednesday, the president said the absence of North Korean nuclear threats through peaceful reunification of the Korean Peninsula is crucial for security in the Indo-Pacific region.

"The reality of global politics largely deviates from the principle," Yoon said during the 47th Singapore Lecture on Wednesday at Orchard Hotel Singapore.

"It is difficult to assure that the reality in the Indo-Pacific tomorrow would be different from that in Ukraine or the Middle East today," Yoon also said.

Attention is also being paid to whether Seoul would comment on disputes in the South China Sea.

Yoon said during the Singapore Lecture on Wednesday that South Korea and China are on their path to "recovery at all levels."

He also said Seoul and Beijing are building a relationship together "pursuing common interests based on mutual trust and rules-based international order."

But on Monday, a joint declaration between South Korea and the Philippines -- unveiled as Yoon met his counterpart Ferdinand Marcos Jr. -- stated that the two countries "emphasized the universal and unified character" of the 1982 United Nations Convention on the Law of the Sea.

The two countries also recognized that the UNCLOS "sets out the legal framework within which all activities in the oceans and seas must be carried out."

A 2016 ruling at the arbitral tribunal, convened under Annex XII to the UNCLOS, unanimously found in favor of the Philippines over its territorial dispute with China in the South China Sea.

In this vein, Marcos stressed during his meeting with Yoon a need for a concerted effort to preserve the international maritime order under UNCLOS.

Meanwhile, Yoon is anticipated to hold bilateral talks with Ishiba on the margins of the ASEAN Summit. The leaders seek to improve ties and overcome long-running territorial and historical disputes. Yoon's office had yet to confirm that the meeting would take place as of press time, but it had previously stated Seoul was in talks with Tokyo.

An official of the presidential office, speaking on condition of anonymity, played down the possibility that Ishiba's "Asian NATO" proposal would emerge during his possible meeting with Yoon, calling it "unrealistic."

Before Ishiba came to power, Yoon met Ishiba's predecessor Fumio Kishida 12 times to gesture at the thawing relationship between the East Asian neighbors.