"We have deep concerns about El Salvador’s democracy, in light of the National Assembly’s vote to remove constitutional court judges," Harris wrote on Twitter. "An independent judiciary is critical to a healthy democracy – and to a strong economy."
Harris' tweet comes as members of her own party try to increase the number of Supreme Court justices on the bench from nine to 13 in order to flip the ideological composition of the court.
"We are on the verge of a crisis of confidence in the Supreme Court," Harris said in March 2019. "We have to take this challenge head-on, and everything is on the table to do that."
Biden, in April, issued an executive order forming a commission to study potential changes to the Supreme Court.
Biden, under pressure from liberals to expand the size of the high court, promised to create the commission during a "60 Minutes" interview back in October in the wake of Justice Ruth Bader Ginsburg's death.
The 36-member commission will be bipartisan and will hold public meetings to evaluate court reforms. The new panel will have 180 days from the first meeting to complete its report on the pros and cons of court reforms.
Fox News' Marisa Schultz contributed to this report.