Tensions between two top Donald Trump economic advisers spilled over during a recent trip to China earlier this month, resulting in what was described by administration officials as a “screaming match.”

The confrontation, which took place between Treasury Secretary Steve Mnuchin and White House economic adviser Peter Navarro, came during a very important stretch of trade negotiations for this White House. And it underscored the deep divisions that have developed within the president’s economic team over a key pillar of the president’s agenda.

Navarro, a hardliner on trade, and Mnuchin, representative of the free-trader camp, have been at loggerheads for weeks over trade negotiations with China. That animus has grown deeper as it’s become clearer that the White House’s strongest protectionist voices are losing the internal argument.

According to four sources familiar with the matter, on the Thursday of the official visit, the U.S. team of principals—including Mnuchin, Navarro, Commerce Secretary Wilbur Ross, U.S. Trade Representative Robert Lighthizer, and chief White House economist Larry Kudlow—had scheduled meetings with Chinese officials.

The following day, Mnuchin, according to two sources, held a closed-door meeting with his Chinese counterpart, without the other U.S. officials, forgoing two negotiating sessions featuring the full U.S. delegation that Navarro wanted. After he caught wind of Mnuchin’s one-on-one, Navarro exploded at the Treasury secretary. The confrontation devolved into several minutes of sniping, swearing, several “fucks,” and insults hurled between the two men. The confrontation happened on the lawn in front of the building where the talks were being conducted, according to a person familiar with what took place.

The White House did not respond to comment on the exchange of words. News of the confrontation was first reported by Axios.

Another source familiar with the verbal argument characterized the incident on the China excursion as more of a “tense confrontation” between the two senior officials. Sources also noted that a similarly heated disagreement went down between Navarro and Ross during the visit to China.

However, people familiar with the incident and general internal feuding note that the true target of Navarro’s ire is Trump’s Treasury secretary.

Mnuchin and Navarro differ sharply on key Trump trade agenda items. Most recently, they have feuded over Trump’s stated openness to easing punitive measures on Chinese electronics firm ZTE Technologies—measures that were designed to punish the company for violating U.S. sanctions on Iran and other nations.

According to those close to Navarro, he sees Mnuchin as the leading advocate of such a move, which Navarro considers anathema to the tough stance toward China that he has encouraged the president to take since assuming office.

On Wednesday, Bloomberg reported that Navarro has been excluded from trade talks with China on Thursday. Other leading Trump economic advisers are expected to fill out the U.S. delegation, potentially including Mnuchin, Lighthizer, and Ross.

The Daily Beast confirmed that Kudlow was also set to be in attendance—and that Navarro was not.

However, following publication of this story, a White House official claimed that Navarro would now, in fact, be granted a seat at the table.

This piece has been updated with additional reporting.