WASHINGTON (Reuters) -- Democratic U.S. Sen. Robert Menendez of New Jersey has been advised by federal officials that he is likely to face corruption-related criminal charges, perhaps as soon as Wednesday, according to a source familiar with the matter.

Menendez is the top Democrat on the Senate Foreign Relations Committee. A second source familiar with the matter said any criminal charges would be brought by federal prosecutors in Florida.

The charges are expected to relate to his dealings with a donor and friend, Florida-based ophthalmologist Salomon Melgen, according to the first source and media reports.

Menendez has been dogged this month by reports that the U.S. Justice Department plans to charge him with corruption, namely that he used his office to promote Melgen's business interests.

Multiple law enforcement sources have been saying since last year that FBI investigators in New Jersey and Florida were conducting an in-depth probe of Menendez's activities.

Politico reported earlier on Tuesday that an indictment could come on Wednesday.

The Justice Department in Washington declined to comment. A representative of the U.S. Attorney’s office in Miami said it was Justice Department policy to neither confirm nor deny the existence of any criminal investigation.

A spokeswoman for Menendez said on Tuesday that she would not comment on "the latest anonymous and illegal leak."

Abbe Lowell, at Chadbourne & Parke LLP, the lawmaker's lawyer, did not immediately respond to a request for comment.

Menendez has maintained that he has done nothing wrong and says he had no plans to leave his Senate seat. He has described his relationship with Melgen as a close friendship.

The Associated Press reported on Monday that federal charges also could be issued against Melgen in connection with the probe.

Menendez, who previously chaired the foreign relations panel, spent 13 years in the House of Representatives and was re-elected to his Senate seat in 2012. He is Cuban-American and one of the most senior Hispanic politicians in the country.

At times, he has been a fierce critic of the Obama administration's foreign policy, particularly on Cuba and Iran. But he is a strong supporter of the White House on other issues.