NEWARK, N.J. — U.S. Sen. Bob Menendez reacted angrily and threatened to use his position on the Senate finance committee when his entreaties about changing Medicare reimbursement policy were rejected, a former Medicare official testified Monday at Menendez’s bribery trial.

The New Jersey Democrat didn’t mention co-defendant Salomon Melgen in either a 2009 phone call or a 2012 meeting about the dispute, former Centers for Medicare and Medicaid Services official Jonathan Blum testified. But Blum said it was clear the Florida eye doctor’s billing dispute was the issue.

An indictment charges Menendez with accepting private jet flights and luxury hotel stays from Melgen in exchange for political influence. Both men have denied the charges and say the gifts stem from their longtime friendship, which extends back to the early 1990s.

While Menendez has claimed in court filings that he sought out then-Health and Human Services Secretary Kathleen Sebelius — who attended the 2012 meeting — because of inconsistencies in Medicare billing practices, prosecutors allege he was acting solely on Melgen’s behalf.

According to Blum, the 2009 phone call started off cordially, but soon turned icy.

“As I did not yield on his statement that the agency wasn’t being consistent, his tone became more hostile,” Blum said. “It was definitely a call that stands out to me. The tone was very angry. I could tell he was not happy with my answers.”

On cross-examination by Melgen’s attorney, Blum added, “I think both of us were frustrated with the call.”

After the 2012 meeting with Sebelius, Blum said, Menendez said he “was going to use the authority he had as a member of the Senate finance committee” to continue to press the issue.

Menendez didn’t mention Melgen by name either time, Blum testified, though then-Senate Democratic Majority Leader Harry Reid mentioned at the 2012 meeting that he had become familiar with the billing issue after talking to Melgen. Blum added that unlike other queries from members of Congress, no other doctors or other potentially affected stakeholders were mentioned in the conversations.

Last week, former Democratic U.S. Sen. Tom Harkin of Iowa, who led a Senate health committee at the time, testified Menendez set up a meeting between him and Melgen about the Medicare billing issue in 2011 but that he didn’t offer assistance.

Melgen eventually paid back $8.9 million to Medicare in the dispute. In a separate case not involving Menendez, Melgen was convicted in Florida in April on multiple counts of health care fraud, submitting false claims and falsifying patients’ records. Sentencing in that case was postponed until after the current trial concludes.