WASHINGTON – Sen. Robert Menendez acknowledged Thursday that his office contacted U.S. health agencies in a way that would help the biggest political donor to his re-election, the same eye doctor whose private jet Menendez used for two personal trips to the Dominican Republic.

But the senator denied that he sought to intervene improperly in billing disputes between the doctor and the government.

Menendez, D-N.J., said he contacted the U.S. Centers for Medicare & Medicaid Services to ask about billing practices and policies. The contacts came during a dispute between CMS and Dr. Salomon Melgen, a longtime friend and campaign supporter of Menendez. The FBI searched Melgen’s 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 of that and to make sure, in doing so, providers would understand how to attain themselves,” Menendez said.

The senator called federal health officials in 2009 and met with them again in 2012, each time urging them to change what he called an unfair payment policy that had cost his friend Melgen $8.9 million, according to an official close to the investigation who spoke on condition of anonymity.

The official said Medicare held firm on the billing dispute and ordered the money repaid. Melgen currently is appealing his case.

Medicare providers accused of fraudulent or improper billing are allowed to appeal their case, even after being fined or suspended from the program.

Melgen contends he didn’t fraudulently bill the taxpayer-funded Medicare program but was confused about what was allowed, the official said.