U.S. Sen. Bob Menendez returned to court Monday and entered a not guilty plea to a charge alleging that he conspired to act as an agent of the Egyptian government when he chaired the Senate Foreign Relations Committee.

Menendez, 69, made the plea during his first appearance before Judge Sidney H. Stein at Manhattan federal court. Stein is expected to preside over a trial tentatively scheduled for May.

Stein said the plea was the sole purpose for the hearing and adjourned the preceding after about five minutes.

The New Jersey Democrat stepped down from his powerful post leading the Senate committee after he was charged last month. Prosecutors said the senator and his wife, Nadine Menendez, accepted bribes of cash, gold bars and a luxury car over the past five years from three New Jersey businessmen in exchange for a variety of corrupt acts.

The other defendants entered not guilty charges to a superseding indictment last week. The senator was permitted to delay his arraignment so he could tend to Senate duties. He has said that throughout his life he has been loyal to the United States and that he will prove he is innocent.

Menendez has resisted calls from more than 30 Democrats to resign.

MORE: Updated indictment accuses Sen. Menendez of being an unregistered agent of Egypt's government

The rewritten indictment added a charge alleging that the senator, his wife and one of the businessmen conspired to have Menendez act as an agent of the government of Egypt and Egyptian officials.

As a member of Congress, Menendez is prohibited from acting as an agent for a foreign government.

Menendez is accused of passing information to the Egyptians about the staff at the U.S. embassy in Cairo, ghostwriting a letter on Egypt's behalf intended to influence fellow senators and urging the U.S. State Department to get more involved in international negotiations to block a dam project Egypt opposed, among other things.

Last week, Nadine Menendez and a businessman, Wael Hana, pleaded not guilty to the superseding indictment.

Both of them were charged with conspiring with the senator to use him as an agent of the government of Egypt and its officials. The charge carries a potential penalty of up to five years in prison.