SINGAPORE, The mood for a thaw in U.S.-North Korea ties that has emerged after their historic summit is expected to pose a tricky geopolitical question to China: what if its traditional ally falls into the orbit of its core competitor?

U.S. President Donald Trump and North Korean leader Kim Jong-un held a historic summit in Singapore on Tuesday, with China carefully watching the encounter seen as a major step toward addressing the deep-rooted enmity between the longtime foes.

After the summit, Trump said Washington's relationship with Pyongyang will be "much different" from what it was, with Kim predicting that "the world may see a major change."

The tete-a-tete came amid an intensifying strategic competition between the United States and China over a raft of nagging issues, ranging from trade and maritime security to intellectual property and human rights records.

"China may think that reconciliation between the U.S. and North Korea could lead to a reduction in its influence over the Korean Peninsula and undermine its leverage to keep America in check in the regional geopolitical context," said Park Won-gon, a security expert at Handong Global University.

"Though China may not try to play any spoiler role in the rapprochement process, it will strive to maintain its leverage over its traditional ally," he added.

In the lead-up to the summit, Beijing was seen scurrying to improve ties with Pyongyang following years of estrangement caused by the isolated regime's unceasing saber rattling, including nuclear and long-range missile tests.

China has provided aircraft for the North Korean leader to fly to the summit venue in the Southeast Asian state, a sign that it would like to maintain its presence as the North's critical patron, analysts said.

After years of his arm's-length diplomacy, Chinese President Xi Jinping held two summits with the North Korean leader in March and May, at which they stressed their countries' checkered relationship "forged in blood."

After Xi took power in 2012, Xi was seen recalibrating China's approach toward the provocative neighbor, shunning top-level exchanges and participating in U.S.-led sanctions, which were triggered by the North's provocations.

The shift in the approach came amid Washington's beefed-up calls for the Asian great power to play a role as a "responsible regional stakeholder" and a growing sense within China that its wayward ally was becoming a strategic liability rather than an asset.

China under Xi's leadership has apparently pursued a different foreign policy identity -- a great power rather than a developing country. With that new identity, China has sought close ties both with Seoul and Pyongyang -- a move that apparently unnerved its ally.

But observers said the Chinese leader recently made a course correction amid recognition that it could lose trust with the North, seen as a buffer state that could prevent the advance of U.S. troops in the South all the way to its doorstep.

China's relations with the South also soured in recent years, after it took apparently retaliatory action against South Korean businesses in response to Seoul's decision to host a U.S. missile defense battery.

"In some sense, as China is focused on great-power diplomacy, there appeared to have been a loss of delicate attention toward South and North Korea," said Suh Jin-young, professor emeritus of Korea University.

"After all, China had been diplomatically discourteous to the South (with suspected economic retaliation) while it had failed to gain trust from the North. There might have been a reflection on this within China," he added.

Amid a flurry of diplomacy on the North, which was triggered by the liberal government in Seoul, Beijing has been seen as wary of being sidelined or marginalized.

A wake-up call for Beijing was the April 27 inter-Korean summit declaration in which South Korean President Moon Jae-in and Kim agreed to seek a formal end to the 1950-53 Korean War, possibly through a three-way summit that excludes China.

Apparently mindful of the possibility that it could be alienated in the process of ending the war, China's foreign ministry said it would play a "suitable" role as a signatory to the Armistice Agreement, which halted the armed conflict, but left the two Koreas technically at war.

The improvement in relations between Washington and Pyongyang could serve the strategic interests of China, some analysts said, as it could raise the need for a reduction of the American military footprint in the South.

"Should U.S.-North Korea relations improve, this would bring about peace on the peninsula and could raise the need to alter the status of the U.S. forces in Korea," Nam Chang-hee, a security expert at Inha University, said.

"In that process, there could be an attenuation of the South Korea-U.S. alliance and possibly the prospect of the withdrawal of the U.S. forces, which is something China has probably wanted to see," he added.

Source: Yonhap News Agency