The new indictment alleges Mr Menendez and his wife Nadine, provided "sensitive US government information" that helped Egypt's government.
This comes weeks after the couple were accused of bribery, which they pleaded not guilty to.
The senator called the accusations false and has denied any wrongdoing.
In September, prosecutors charged Mr Menendez and his wife Nadine with accepting bribes of cash, gold, payments toward a home mortgage and a luxury vehicle from three New Jersey businessmen as part of a scheme to use the senator's influence to increase US aid and military sales to Egypt.
During a search of the senator's New Jersey home last year, investigators found $480,000 (£393,000) in cash hidden throughout the residence, as well as 13 bars of gold bullion worth an estimated $155,000 (£127,000), prosecutors allege.
The new indictment filed by New York federal prosecutors on Thursday alleges Mr Menendez used "his influence and power to breach his official duty in ways that benefited the Government of Egypt".
While part of the Senate Foreign Relations Committee - which he has now stepped down from - he allegedly encouraged fellow senators to lift a hold on $300m (£246m) in aid to Egypt and provided sensitive US government information to its government, according to prosecutors.
The indictment alleges the conspiracy occurred between January 2018 and June 2022.
It also includes new photos of Mr Menendez and his wife, Nadine, dining with Egyptian officials at a steakhouse in Washington, DC. Nadine asked: "What else can the love of my life do for you?" prosecutors alleged.
According to the indictment, "public officials, including Members of Congress, are prohibited from agreeing to be or acting as an agent of a foreign principal required to register under FARA", which is the Foreign Agents Registration Act.
In last month's indictment, the pair each face three criminal counts: conspiracy to commit bribery, conspiracy to commit honest services fraud, and conspiracy to commit extortion under colour of official right.
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