A bipartisan group of US senators urged President Joe Biden to punish Venezuela’s Nicolas Maduro for attacks against his top opposition rival, saying that an upcoming election fails to meet the promise of a free and fair vote.

Maryland Democrat Ben Cardin, the chairman of the Senate Foreign Relations Committee, and Republicans Marco Rubio of Florida and Bill Cassidy of Louisiana cited “serious concerns” about the integrity of the process leading up to the presidential election scheduled for July.

The US must “consider individual sanctions for those directly responsible for the repressive actions,” the senators said in a statement. “The United States and the international community must respond swiftly and hold the regime accountable.”

The Biden administration suspended sanctions on Venezuela’s oil and gas industry for six months in October after the Maduro government and opposition reached an agreement for fresh elections. The suspension is set to expire on April 18, and the US has repeatedly said that it won’t provide an extension unless Venezuela lives up to its side of the deal.

But in the months since reaching the agreement, Maduro barred the opposition’s primary winner, Maria Corina Machado, and her substitute, Corina Yoris, from running and arrested nine of Machado’s top aides.

The crackdown has been so severe that even allies in Colombia and Brazil have publicly condemned Maduro actions against the opposition.