Mexico said Friday it is sending a diplomatic note protesting supposed U.S. interference after the American ambassador openly criticized a proposed Mexican judicial overhaul that would make all judges stand for election.

President Andrés Manuel López Obrador called the comments “disrespectful of our national sovereignty” and claimed it interfered in Mexico’s domestic affairs, adding “I hope this will not happen again.”

On Thursday, U.S. Ambassador Ken Salazar said the proposed changes pose a “risk” to Mexico’s democracy and that they threaten “the historic commercial relationship” between the two countries. Critics fear the constitutional changes are an attempt by López Obrador to weaken the independence of the judiciary.

The diplomatic note said the ambassador’s comments “represent an unacceptable interference, a violation of Mexico’s sovereignty.”

The proposal to require judges to stand for election, which has not been approved yet, has spurred criticism from investors and financial institutions in recent days, with the Mexican peso steadily dropping in currency markets.

On Tuesday, Morgan Stanley downgraded its recommendation for investing in Mexico, saying the overhaul would “increase risk.” Others, like Citibanamex, warned that passage of the proposal could end in the “cancellation of liberal democracy.”

“Democracies can’t function without a strong, independent and non-corrupt judicial branch,” Salazar told reporters. “Any judicial reform needs to have safeguards that the judicial branch is strengthened, and not the subject to political conditions.”

He said the proposed overhaul would “help cartels and other bad actors take advantage of inexperienced judges with political motivations,” and “create turbulence” both economically and politically for years to come

The proposed overhaul also has triggered strikes by federal court workers and judges in many parts of Mexico this week.