Sen. Robert Menendez admitted contacting government agencies on behalf of a donor and friend, but denied acting improperly.

The senator from New Jersey said he did contact U.S. health agencies to help Dr. Salomon Melgen, his biggest political donor who flew him twice on his private jet to the Dominican Republic.

But Menendez denies he sought to intervene improperly in billing disputes between the doctor and the government.

Menendez said Thursday he contacted the Centers for Medicare & Medicaid Services to ask about billing practices. This was during a dispute between CMS and Salomon Melgen, a longtime friend and donor. The FBI searched Melgen's Florida offices last week.

"The bottom line is, we raised concerns with CMS over policy and over ambiguities that are difficult for medical providers to understand, and to seek a clarification," Menendez said.

A week before the November election, The Daily Caller, a conservative website, reported that Menendez had used a business jet owned by Melgen, an eye doctor of Dominican descent, to fly to the Dominican Republican for trysts with prostitutes. None of the allegations have been substantiated. It is unclear whether the FBI raid of Melgen's office was related to Menendez.

The reports have dogged Menendez, 59, as he has assumed the chairmanship of the Senate Foreign Relations Committee, succeeding former Sen. John Kerry, who resigned last week to become secretary of state. The Senate Ethics Committee is investigating the case.

Based on reporting by The Associated Press.

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