Republican presidential nominee and former U.S. President Donald Trump, left, and Republican vice presidential candidate Senator J.D. Vance of Ohio, arrive at the Republican National Convention in Milwaukee, Wis., Tuesday (local time). The convention comes just a few days after a 20-year-old Pennsylvania man attempted to assassinate Trump. EPA-Yonhap

Korea may face renewed pressure to increase its defense-cost sharing with the United States if former President Donald Trump secures a second term, a scenario that some observers consider increasingly likely following his survival of a recent assassination attempt.

In recent months, Trump and his former aides have hinted through media interviews and speeches that Seoul should increase its contribution to the stationing of the 28,500 U.S. Forces Korea (USFK) troops stationed there.

The latest comments came from Robert O'Brien, who served as national security adviser during the Trump administration from 2019 to 2021. He emphasized that Korea, a "wealthy nation," should make a "big contribution" to defense-cost sharing.

"South Korea can afford to pay for its defense," O'Brien told Korean reporters in Milwaukee, Wis., Tuesday (local time), where the Republican National Convention is underway through Thursday.

"We look forward to seeing a big contribution from South Korea, which is already doing great with its Navy, Army, and military equipment. I'm sure they'll have the money to cover whatever defense needs they have," he was quoted as saying by Yonhap News Agency.

O'Brien's remarks come as Seoul and Washington concluded the fifth round of the 12th Special Measures Agreement (SMA) negotiations last Friday. The agreement, once finalized, would outline Korea's financial obligations for stationing USFK troops starting from 2026, as the current six-year SMA is set to expire at the end of 2025.

During his first term, Trump demanded that Korea increase its share of defense costs from $900 million to $5 billion. The stalled negotiations were eventually resolved in March 2021 after the Biden administration took office, resulting in Korea agreeing to pay 1.18 trillion won ($854 million), marking a 13.9 percent increase from the 2019 agreement and the third-largest annual increase for Seoul since the pact began in 1991.

Cha Du-hyeogn, a senior researcher at the Asan Institute for Policy Studies, warned that the defense cost-sharing agreement could face significant upheaval if Trump is re-elected.

"Even if the two sides succeed in finalizing the SMA deal, there's a possibility that Trump, once back in the White House, may try to nullify the already-signed agreement," Cha told The Korea Times, Wednesday.

Robert O'Brien, left, who served as the national security adviser during the former Donald Trump administration, poses with Korean Ambassador to the U.S. Cho Hyun-dong at the Republican National Convention in Milwaukee, Wis., Tuesday (local time). Yonhap

In a separate interview with Bloomberg Businessweek published also on Tuesday, Trump stated that Taiwan should pay the U.S. for defense protection.

"Taiwan should pay us for defense," Trump was quoted as saying. "You know, we're no different than an insurance company. Taiwan doesn't give us anything."

Although Trump did not mention Korea in the interview, these comments reflect his stance on partners in the East Asian region, Cha said.

"Our government should prepare better strategies with logical data, showing that we have been paying a fair amount of defense costs," the researcher suggested.

Cha viewed that Trump's rhetoric about allies "free-riding" on U.S. defense is a campaign strategy to appeal to American voters, and it is often based on distorted information. However, this message seems to resonate with many of his supporters who believe that the U.S. is currently overly engaged in international issues.

Officials in Seoul have been closely monitoring the U.S. election as the potential re-election of Trump could significantly impact the trajectory of bilateral relations with Washington, which have been bolstered under incumbent President Joe Biden.

Korean Ambassador to the U.S. Cho Hyun-dong attended the Republican National Convention in Milwaukee and engaged with Trump's key aides. The embassy stated that Cho's attendance was at the invitation of the Republican Party to foreign missions in Washington, D.C.