WASHINGTON (AP) — Sen. Bob Menendez, under federal investigation for his relationship with a Florida doctor and political donor, is expected to face criminal charges in the coming weeks, a person familiar with the matter said Friday.

The disclosure came as Menendez, a New Jersey Democrat, said he will answer questions from reporters in his home state after his office issued a statement saying all of his actions have been appropriate and lawful.

The person discussed the expected filing of charges on condition of anonymity because the investigation is pending.

The Justice Department's decision to move forward with a criminal case was first reported by CNN. Attorney General Eric Holder, in South Carolina with President Barack Obama on Friday, declined to say whether he has authorized criminal charges against the senator.

Menendez, who served for more than a decade in the House of Representatives before his election to the Senate in 2006, is the top Democrat on the Senate Foreign Relations Committee. He has been critical of the Obama administration's negotiations with Iran on its nuclear program and outspoken in opposition to normalizing relations with Cuba.

He has been dogged for more than two years by questions about his ties to Dr. Salomon Melgen, a Florida ophthalmologist as well as a friend and political donor whose medical office was raided by Florida authorities two years ago.

In particular, Menendez has faced questions about trips he took to the Dominican Republic aboard Melgen's private plane. He has acknowledged taking several actions that could have appeared to benefit Melgen, including contacting the Medicare agency to urge changes to a payment policy that had cost Melgen millions.

His failure to reimburse Melgen for flights between New Jersey and the Dominican Republic on the eye doctor's Canadair Challenger 600s luxury jet was the first serious signal of Menendez' legal troubles in early 2013. Menendez and Melgen had flown at least twice in 2010 between New Jersey to the Dominican Republic, but the trips had gone without reimbursement for more than two years.

The flights were just one vestige of the close relations between Menendez, who took over the powerful Senate Foreign Relations Committee in 2013 when previous chair John Kerry left to become Secretary of State, and Melgen, a multimillionaire who was willing to lavish campaign donations on his friend and allied causes.

The two men often appeared together at Democratic Party and Latino political functions from Washington to Miami. Melgen contributed nearly $200,000 to Democratic Party candidates since 1998, including $14,200 directly to Menendez. And in 2012, during Menendez' re-election campaign, Melgen gave $700,000 to the Majority PAC, a super political action committee for Democratic Senate candidates; the PAC spent more than $580,000 to aid Menendez' campaign.

Menendez has reimbursed Melgen for three plane trips. Last year, the senator disclosed that his campaign accounts had paid a law firm $250,000 for legal costs related to Justice Department and Senate Ethics Committee investigations of his ties to the Floridian.

For his part, Melgen earned renewed scrutiny when government data last year showed he had gotten more money in Medicare reimbursements in 2012 than any other doctor in the country

Menendez's spokeswoman, Tricia Enright, earlier issued a statement saying "any actions taken by Senator Menendez or his office have been to appropriately address public policy issues and not for any other reason."

She said Menendez and Melgen have long been friends and attended one another's family events and exchanged personal gifts.

"We know many false allegations have been made about this matter, allegations that were ultimately publicly discredited. We also know that the official investigation of this matter is ongoing, and therefore cannot address allegations being made anonymously," Enright added.

A glimpse into the investigation emerged last week, when it was revealed that a federal appeals court had ordered a hearing to determine whether two of Menendez' aides should be compelled to testify before a grand jury about the senator's efforts on behalf of Melgen.

The New Jersey Law Journal reported that the appeals court identified two issues in question: A billing dispute Melgen had with the Centers for Medicare and Medicaid Services and a deal he had to sell port screening equipment to the government of the Dominican Republic.

The aides have declined to testify about some actions they took, citing a constitutional provision saying a lawmaker can't be questioned about legislative acts anywhere except in Congress. A U.S. district judge ruled previously they should testify because their actions weren't legislative in nature, the journal reported. It said the 3rd U.S. Circuit Court of Appeals disagreed, and the question remains unresolved.

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Associated Press writers Nedra Pickler in Columbia, South Carolina, Erica Werner in Washington and Dave Porter in Newark, New Jersey, contributed to this report.