NEWARK, N.J. » U.S. Sen. Bob Menendez, under federal investigation for his relationship with a Florida doctor and political donor, defiantly said Friday he has always been honest in office even as a person familiar with the matter said he’s expected to face criminal charges soon.

"Let me be very clear, I have always conducted myself appropriately and in accordance with the law," Menendez, a New Jersey Democrat, said at a press conference in his home state. "Every action that I and my office have taken for the last 23 years that I have been privileged to be in the United States Congress has been based on pursuing the best policies for the people of New Jersey and this entire country."

The person who discussed the expected filing of charges against Menendez in the coming weeks did so on the condition of anonymity because the investigation is pending. Attorney General Eric Holder declined to say whether he has authorized criminal charges against the senator.

Menendez spoke in English and Spanish, chopping his hand down for emphasis and declaring he’s "not going anywhere." He said he couldn’t take questions "because there is an ongoing inquiry."

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

He has been dogged by questions about his ties to Dr. Salomon Melgen, an ophthalmologist whose office was raided by authorities two years ago.

The scrutiny has focused on trips Menendez 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 a Medicare agency to urge changes to a payment policy that had cost Melgen millions of dollars.

Menendez said he has been friends with Melgen for two decades.

"We celebrated holidays together," he said. "We have been there for family weddings and sad times like funerals and have given each other birthday, holiday and wedding presents just as friends do."

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

After news reports in early 2013 raised concerns about the flights’ non-payments, ethics watchdogs complained to the Senate Ethics Committee, which agreed to review the cases. Prompted by the Senate’s scrutiny, Menendez agreed to reimburse Melgen $58,500.

Menendez’s office later disclosed a third flight, from Florida to New Jersey in 2011, saying he had repaid Melgen $11,250 for it.

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

The flights were just one vestige of the close relations between Menendez 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 to Menendez. And in 2012, during Menendez’s re-election campaign, Melgen gave $700,000 to a super political action committee that spent more than $580,000 to help Menendez.

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.

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.

Tucker reported from Washington. Associated Press writers Nedra Pickler in Columbia, South Carolina, and Erica Werner in Washington contributed to this report.