Sen. Bob Menendez pleaded not guilty in federal court Monday to a charge alleging he conspired to act as a foreign agent of Egypt.

The New Jersey Democrat personally entered his plea before district Judge Sidney H. Stein.

Menendez, his wife Nadine Arslanian Menendez, and three other co-defendants were indicted last month on corruption-related offenses and are accused of accepting "hundreds of thousands of dollars in bribes" in exchange for the senator's influence -- specifically on issues to benefit Egypt. Menendez and the others pleaded not guilty to those charges. A trial date has been set for May.

The additional charge unveiled early this month in a superseding indictment filed against Menendez, who was chairman of the Senate Foreign Relations Committee at the time of the alleged actions, adds a new dimension to the case by alleging a US senator was working on behalf of another country.

Prosecutors allege Nadine Menendez and businessman Wael Hana failed to register as agents working on behalf of Egypt and conspired to have the senator act on behalf of Egypt. Nadine Menendez and Hana both pleaded not guilty to the superseding indictment last week.

Menendez stepped down as chairman of the Senate Foreign Relations committee last month when he was initially charged but has rejected calls to resign as New Jersey's senior senator.

It is illegal for a member of Congress or any public official to act as foreign agent.

The senator stressed his loyalty to the US in a statement earlier this month, arguing that the new charge goes against his "long record of standing up for human rights and democracy in Egypt and in challenging leaders of that country."

The new charge carries a maximum sentence of five years in prison. Menendez and his wife are now facing as much as 50 years in prison if convicted.