NEWARK, N.J. (CBSNewYork/AP) — The fifth week of the federal bribery trial against U.S. Sen. Robert Menendez (D-New Jersey) got under way in Newark Monday.

After the day started with the defense calling the prosecution’s timeline into question, former Medicare official Jonathan Blum took the stand and testified about a couple of heated exchanges he had with Menendez – one by phone in 2009 and another in person in 2012.

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Blum said during those meetings, an angry Menendez became hostile when Blum did not agree that a Medicare reimbursement should be changed.

The 2012 meeting involved former Health and Human Services Secretary Kathleen Sebelius.

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Blum testified though Menendez did not mention a name, it was clear to him the conversation was about Florida eye doctor Salomon Melgen, who was involved in a multimillion-dollar billing dispute with Medicare.

An indictment charges Menendez with accepting private jet flights and luxury hotel stays from Melgen in exchange for political influence.

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(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)