In this image made from video released by KRT on Tuesday, March 7, 2017, North Korea launches four missiles in an undisclosed location North Korea. On Monday, North Korea fired four ballistic missiles in an apparent protest against ongoing U.S.-South Korean military drills that it views as an invasion rehearsal. KRT via AP Video While the US openly mulls military action against North Korea and its possibly nuclear consequences, another threat looms largely behind: China.

"Broadly speaking, if you asked me a year ago if war between major powers was thinkable, I'd say no. Now I'd say yes," Ian Bremmer, the head of Eurasia Group told Business Insider.

"Not imminent, not likely, but it could happen."

China has a vested strategic interest in maintaining a North Korean state that's unfriendly to the West to act as a buffer state between the powerful, democratic state of South Korea and China's authoritarian mainland.

China may not support North Korea's brutal human rights abuses or their nuclear threats, but it is highly unlikely that the country would stand idly by if the US tried to remove Kim Jong-un, according to Bremmer. A unified, Western-leaning Korea would be a threat to China's efforts to project power throughout the region.

"The US-China relationship will be radically worse if we strike North Korea," said Bremmer. A strike against Pyongyang would "clearly have implications on US markets," with a direct, almost existential risk to South Korea, he added.

And if Trump takes out his frustrations over North Korea on China, it could lead to a dangerous deterioration of relations, and possibly the first major power conflict since World War II, according to Bremmer.

China's President Xi Jinping inspects honour guards during a welcoming ceremony outside the Great Hall of the People in Beijing, China. Reuters/Jason Lee

Even if the US doesn't take military action, the Trump administration's hawkish stance on North Korea could still sour relations between Beijing and Washington, the world's two biggest economies, said Bremmer.

China's hardline conservatives "would love to have an excuse to go harder on the US," he said.

Trump has repeatedly pushed China to put more pressure on North Korea, but China's influence in Pyongyang has been fading.

Kim Jong Un recently executed senior military officials with ties to China, limiting Beijing's influence. Chinese President Xi Jinping did support sanctions on North Korea, so it's unclear what else Trump could demand of Xi.