SEOUL, South Korea >> The national security advisers of the United States, South Korea and Japan called on Saturday for a stronger international push to suppress North Korea’s development of nuclear weapons and missiles and its military cooperation with other countries amid concerns about its alleged arms transfers to Russia.

The meeting in Seoul came as tensions on the Korean Peninsula are at their highest in years, with North Korean leader Kim Jong Un accelerating the expansion of his nuclear and missile program and flaunting an escalatory nuclear doctrine that authorizes the preemptive use of nuclear weapons.

The United States and its Asian allies have responded by increasing the visibility of their trilateral security cooperation in the region and strengthening their combined military exercises, which Kim condemns as invasion rehearsals.

U.S. and Japanese officials said Saturday’s three-way talks would include discussions on North Korea’s recent launch of its first military reconnaissance satellite, which Kim has described as crucial for monitoring U.S. and South Korean military activities and enhancing the threat of his nuclear-capable missiles.

Washington, Seoul and Tokyo have also expressed concerns about a potential arms alignment between North Korea and Russia. They worry Kim is providing badly needed munitions to help Russian President Vladimir Putin wage war in Ukraine in exchange for Russian technology assistance to upgrade his nuclear-armed military.

Following the meeting, U.S. national security adviser Jake Sullivan said Washington will strengthen its coordination with Seoul and Tokyo to respond to North Korean cyber crimes and other efforts to bypass U.S.-led international sanctions aimed at choking off funds going to its nuclear weapons and missile program.

Sullivan held separate bilateral talks Friday with South Korea’s national security office director, Cho Tae-yong, and Japan’s national security secretariat secretary general, Takeo Akiba.

Sullivan also met with South Korean President Yoon Suk Yeol.

At a dinner reception for Sullivan and Akiba on Friday, Yoon said it is critical the three countries continue to build on his August summit with U.S. President Joe Biden and Japanese Prime Minister Fumio Kishida at Camp David, where they vowed to deepen security and economic cooperation.

South Korea’s presidential office said Sullivan during his bilateral meeting with Cho on Friday reaffirmed the United States’ strong commitment to defend its ally in the face of North Korean threats.

Sullivan also expressed support for the South’s recent decision to partially suspend a 2018 inter-Korean military agreement on reducing border tensions, which had established border buffers and no-fly zones, to strengthen front-line surveillance of the North, the office said.

At their one-on-one meeting Friday, Cho and Akiba discussed strengthening trilateral cooperation with Washington and building broader “international solidarity” to respond to North Korea’s nuclear and missile program. They said it poses a threat “not only to the Korean Peninsula, but also to the regional and international community as a whole,” Seoul said.

The U.S., South Korean and Japanese national security advisers last held a trilateral meeting in June in Tokyo.

Speaking to reporters in Tokyo on Thursday, Mira Rapp-Hooper, the White House National Security Council’s senior director for East Asia and Oceania, said the three national security advisers were expected to discuss North Korea’s weapons threats and its recent satellite launch. He said they would also talk about the countries’ “shared perspectives” on cooperation between Pyongyang and Moscow.

“We are very concerned about DPRK-Russia technical as well as political cooperation. We believe that the cooperation between the two, kind of across the spectrum, has the potential to be deeply destabilizing in the Indo-Pacific as well as in other theaters,” Rapp-Hooper said, using the initials of North Korea’s formal name, the Democratic People’s Republic of Korea.

The discussions between the national security advisers in Seoul came after the U.S., South Korean and Japanese nuclear envoys met in Tokyo for separate talks on North Korea.

The nuclear envoys shared their assessments about North Korea’s recent satellite launch and weapons development and discussed ways to more effectively respond to North Korea’s cyber theft activities and other illicit efforts to evade U.S.-led international sanctions and finance its weapons program, the South Korean and Japanese foreign ministries said.

South Korean intelligence officials have said the Russians likely provided technology support for North Korea’s successful satellite launch in November, which followed two failed launches.

North Korea has said its spy satellite transmitted imagery with space views of key sites in the U.S. and South Korea, including the White House and the Pentagon. But it hasn’t released any of those satellite photos. Many outside experts question whether the North’s satellite is sophisticated enough to send militarily useful high-resolution imagery.

Kim has vowed to launch more satellites, saying his military needs to acquire space-based reconnaissance capabilities.

South Korean intelligence and military officials have said North Korea may have shipped more than a million artillery shells to Russia beginning in August, weeks before Kim traveled to Russia’s Far East for a rare summit with Putin that sparked international concerns about a potential arms deal. Both Moscow and Pyongyang have denied U.S. and South Korean claims about the alleged arms transfers.

Associated Press writer Mari Yamaguchi in Tokyo contributed to the report.