An attorney for Menendez entered the plea yesterday before a federal judge in Newark, one day after he promised to be vindicated and declared that he's "not going anywhere."
The criminal charges brought cloud to the political future of the top Democrat and former chairman of the Senate Foreign Relations Committee, who has played a leading role in Congress on matters involving Iran's nuclear program and US efforts to improve ties with Cuba.
Melgen also entered a not guilty plea, and Judge William Walls set a tentative July 13 trial date. He remains free but had to surrender his passport.
The investigation that led to the indictment came into public view when federal authorities raided Melgen's medical offices in 2013. It will almost certainly lead to a drawn-out legal fight between Menendez and a team of Justice Department prosecutors who have spent years investigating his ties to Melgen.
Menendez said he would temporarily step aside from his role as top Democrat on the Foreign Relations Committee but appeared more defiant than ever at a news conference Wednesday.
"I am not going anywhere. I'm angry and ready to fight because today contradicts my public service and my entire life," Menendez told reporters.