Sen. Robert Menendez (D-N.J.), who finds himself in increasing trouble over his use of flights provided by a Florida doctor who is under investigation, said Monday that his failure to disclose those trips was an oversight caused by his hectic schedule.

"I was in a big travel schedule in 2010," he said Monday in an interview with CNN's Dana Bash -- his first extended comments since his late payments were reported last week. "I was the chair of the DSCC, plus my own campaign getting ready for a reelection cycle. And in the process of all of that, it unfortunately fell through the cracks that our processes didn't catch moving forward and making sure that we paid."

"When it came to my attention that payment had not taken place, I personally paid for them in order to meet my obligations," Menendez said.

Menendez failed to pay for two trips taken in 2010 and provided by Salomon Melgen, a doctor whose office was raided recently by the FBI. It is against the rules for members to accept gifts beyond $250 without prior authorization. Menendez cut a $58,500 check for the trips earlier this month, after the trips were reported by the media.

Menendez also called allegations of prostitution on those trips a "smear" campaign by right-wing media that is totally unsubstantiated.

"It's amazing to me that anonymous, nameless, faceless individuals on a Web site can drive that type of story into the mainstream, but that's what they've done successfully," he said. "Now, nobody can find them. No one ever met them. No one ever talked to them, but that's where we're at. So the bottom line is all of those smears are absolutely false and, you know, that's the bottom line."