Jury selection begins in trial accusing top Democrat of accepting bribes and acting as unregistered foreign agent.
Menendez, 70, faces 16 criminal charges and is being tried alongside two New Jersey businessmen in Manhattan federal court.
Menendez sat with his lawyers on Monday and listened as Judge Sidney H Stein told several dozen prospective jurors about the charges.
The judge told them the “sitting US senator from the state of New Jersey” had been charged in a conspiracy in which he allegedly “agreed to accept bribes and accepted bribes”.
Menendez’s wife, Nadine, has also been charged but will be tried separately. All four defendants have pleaded not guilty.
In September, prosecutors accused Menendez and his wife of accepting cash, gold bars and a Mercedes-Benz convertible in exchange for the senator wielding his political influence in New Jersey and helping the governments of Egypt and Qatar.
Authorities said Menendez promised to help Egypt obtain arms sales and other military aid, and helped co-defendant Wael Hana, an Egyptian-American businessman, obtain a lucrative monopoly on the certification of halal meat exports to Egypt.
Prosecutors also said Menendez tried to help his other co-defendant, prominent New Jersey developer Fred Daibes, obtain millions of dollars from a Qatari investment fund, and sought to disrupt a federal criminal case against Daibes in New Jersey.
Much of the cash received by the couple was stuffed inside clothing at their home, prosecutors said.
A few weeks after the initial indictment was unsealed, US authorities in October also charged Menendez – who previously chaired the influential Senate Foreign Affairs Committee – with serving as an unregistered agent of Egypt.
Speaking to reporters in late September, Menendez said he was confident he would be exonerated in the case and would continue his political career.
“I firmly believe that when all the facts are presented, not only will I be exonerated, but I still will be New Jersey’s senior senator,” he said.
He also sought to defend his record on Egypt.
“Throughout my 30 years in the House of Representatives and the Senate, I have always worked to hold accountable those countries including Egypt for human rights abuses, the repression of its citizenry, civil society, and more,” he told reporters at the time.
Menendez is up for re-election in November and has said he might run as an independent if he is exonerated in the criminal case.
But recent polls show he is deeply unpopular among New Jersey voters and many Democratic Party senators, including New Jersey’s Cory Booker, have called for him to resign.
Fewer than one in six voters polled in March by Monmouth University and Emerson College Polling/PIX11/The Hill said they approved of Menendez’s job performance. Even fewer said they would vote for him as an independent.
This is Menendez’s second criminal trial: In 2017, a New Jersey federal judge declared a mistrial after jurors deadlocked on whether he broke the law by providing help to a wealthy ophthalmologist in exchange for lavish gifts and political contributions.