New Jersey Senator Bob Menendez, his wife Nadine Menendez and two other co-defendants named in a corruption case pleaded not guilty to an additional obstruction of justice charge brought against them by federal prosecutors in an arraignment on Monday.

       For the second time in less than a year, Mr Menendez, 70, entered the Daniel Patrick Moynihan federal courthouse in New York City to face an arraignment on charges that accuse him, his wife and two New Jersey businessmen, Wael Hana and Fred Daibes, of participating in a bribery scheme in exchange for political favours.

       After entering the courtroom just before his arraignment, Mr Menendez sat facing forward with his hands in a steeple position. Attorneys for him and his co-defendants flanked him, Ms Menendez, Mr Hana and Mr Daibes. All four were present in the courtroom.

       Last week, federal prosecutors returned a superseding indictment against Mr Menendez, Ms Menendez, Mr Hanna and Mr Daibes – increasing the charges from four to 18 just two months before trial is slated to begin.

       The fresh charges accuse the senator and co-defendants of obstruction of justice, among others, by attempting to repay a former co-defendant for bribes they previously accepted after learning they were under investigation.

       They arrived after the former co-defendant, Jose Uribe, agreed to plead guilty to seven charges and cooperate with the government’s investigation. According to court filings, Mr Uribe told prosecutors as well as the judge overseeing the cases that he lied to investigators and his own lawyer, allegedly at the behest of Ms Menendez.

       This is just a small portion of the wider corruption case against the Menendezes as well as the co-defendants.

       Mr Menendez is accused of accepting bribes, including large sums of cash, gold bars and jewelry, in exchange for using his political influence to enrich Mr Hanna and Mr Daibes and benefit the governments of Egypt and Qatar.

       Federal prosecutors initially charged Mr Menendez with three counts related to the corruption case but in September included a superseding indictment, to add the charge of conspiring to act as a foreign agent to Egypt. In January, prosecutors expanded the initial charges to include Qatar.

       The New Jersey senator has not resigned from his seat yet, though he did step down from his position as chairman of the Senate Foreign Relations Committee.

       When asked whether he would resign or run for re-election on Monday, Mr Menendez responded that he “wouldn’t announce it in a courtroom.”

       Mr Menendez and the co-defendants are scheduled to go to trial on May 6. Judge Sidney Stein declined to move the date of the trial but said it was contingent on whether or not the defence appeals the case and an appeals court issues a stay.

       Michelle Del Rey contributed to this report.