On the eve of China President Xi Jinping’s first visit to the U.S. during the Trump presidency, North Korea—which was already on the summit’s agenda—launched a medium-range ballistic missile early Wednesday morning (local time) in the Sea of Japan. This is Pyongyang’s fourth attempted missile launch this year, and concern continues to grow about the country’s attempts to upgrade its nuclear capabilities. The timing of the launch is a “deep embarrassment” for President Xi, according to the New York Times. China has been North Korea’s closest ally for decades and accounts for almost all of the country’s international trade.

“Any launch of objects using the ballistic missile technology is a violation of U.N. Security Council resolutions but the North has defied the ban as infringement of its sovereign rights to self defense and the pursuit of space exploration,” Reuters reports. “North Korea attempted to launch a ballistic missile two weeks ago from its east coast and earlier in March fired four missiles toward Japan, some of which came as close as [190 miles] to its coast.”

The U.S. believes North Korea is working on—but is still a ways off from producing—an intercontinental ballistic missile (ICBM) capable of hitting the U.S. with a nuclear warhead. The recent uptick in launch activity is particularly alarming for U.S. allies nearby: Japan and South Korea. Even before the launch, U.S. officials were talking tough ahead of President Xi’s arrival, and President Trump has repeatedly said out loud that he believes China should do more to rein in Pyongyang. On Tuesday, Secretary of State Rex Tillerson released this somewhat cryptic statement in reaction to the missile launch:

North Korea launched yet another intermediate range ballistic missile. The United States has spoken enough about North Korea. We have no further comment.

That appears to be a subtle rebuke of previous administration’s attempts to get North Korea to stand down, and a possible indicator that new, more direct military options may be under consideration. “The clock has now run out, and all options are on the table,” a senior White House official told reporters Tuesday.