President Donald Trump. Win McNamee President Donald Trump has made it very clear that when he meets with Chinese President Xi Jinping on Thursday, one topic will tower above the rest: North Korea's nuclear posturing.

But Trump, whose administration has gone further than any before it in stressing the potential for a military strike on North Korea, may be running out of time to determine North Korea's fate on his own terms.

As North Korea continues to test nuclear weapons and ballistic missiles, the US nears a "point of no return," Omar Lamrani, a senior military analyst at Stratfor, a geopolitical analysis firm, told Business Insider.

Essentially, once North Korea's military perfects an intercontinental ballistic missile that can strike the US mainland, the US would no longer be able to launch a preemptive military attack without fear of casualties at home, and it may then consider recognizing North Korea's Kim Jong Un for the first time as a legitimate world leader.

But perfecting an ICBM could take years, and South Korean politics could freeze Trump out of the conversation long before then.

"If the Trump administration is hell-bent on significantly stepping up pressure on China and North Korea, it's going to have a serious problem," Joel Wit, a former State Department diplomat who cofounded 38North, a website that brings together experts on North Korea, told Business Insider.

That problem's name is Moon Jae-in, a liberal South Korean human-rights lawyer who is favored to win the country's May 9 presidential election.

"He is going to pursue a very different approach from President Park," Wit said, referring to Park Guen-hye, South Korea's conservative former president who was recently impeached and arrested after a bizarre influence-peddling scheme came to light.

Wit said the normally ironclad alliance between the US and South Korea could be rocked by a reversal by Moon on policy toward North Korea. Moon is expected to pursue some kind of diplomacy with North Korea, a strategy that has been attempted previously in the past-quarter century to no success.

A missile test guided by North Korean leader Kim Jong Un in an undated photo released by North Korea's Korean Central News Agency on February 13. KCNA/Handout via Reuters

This couldn't contrast any more with public stances from officials in the Trump administration that the "clock has now run out" on Pyongyang and "the United States has spoken enough about North Korea."

Wit said the clash in objectives for North Korea would create "problems that the Chinese can take advantage of," further relegating the US to the sidelines without the North making a single concession.

So if Trump can't convince Xi he's on the brink of war with North Korea and muscle out some concessions, he's looking at about a one-month window in which he could act unilaterally, before possible responses go from bad to worse.