PANAMA CITY — U.S. Secretary of State Marco Rubio brought a warning to Panamanian leader José Raúl Mulino on Sunday: Immediately reduce what President Donald Trump says is Chinese influence over the Panama Canal area or face potential retaliation from the United States.

Rubio, traveling to the Central American country and touring the Panama Canal on his first foreign trip as top U.S. diplomat, held face-to-face talks with Mulino, who has resisted pressure from the new U.S. government over management of a waterway that is vital to global trade.

Speaking on behalf of Trump, who has demanded that the canal be returned to U.S. control, Rubio told Mulino that Trump believed that China’s presence in the canal area may violate a treaty that led the United States to turn the waterway over to Panama in 1999. That treaty calls for the permanent neutrality of the American-built canal.

“Secretary Rubio made clear that this status quo is unacceptable and that absent immediate changes, it would require the United States to take measures necessary to protect its rights under the treaty,” the State Department said in a summary of the meeting.

Mulino, meanwhile, called his talks with Rubio “respectful” and “positive” and said he did not “feel like there’s a real threat against the treaty and its validity.”

The president did say Panama would not be renewing its agreement with China’s Belt and Road Initiative when it expires. Panama joined the initiative, which promotes and funds infrastructure and development projects that critics say leave poor member countries heavily indebted to China, after dropping diplomatic recognition of Taiwan and recognizing Beijing.

Rubio later toured the canal at sunset with its administrator, Ricaurte Vásquez, who has said the waterway will remain in Panama’s hands and open to all countries. Rubio crossed the lock and visited the control tower, looking down over the water below, where a red tanker was passing through.

Earlier, about 200 people marched in the capital, carrying Panamanian flags and shouting “Marco Rubio out of Panama,” “Long live national sovereignty” and “One territory, one flag” while the meeting was going on. Some burned a banner with images of Trump and Rubio after being stopped short of the presidential palace by riot police.