The 72-year-old Callejas, who has been on bail in the United States since leaving Honduras by private jet late last year to face justice, will be sentenced on August 5.
The two counts each carry a maximum sentence of 20 years in jail.
"Guilty," Callejas told Magistrate Judge Robert Levy in a US federal court in Brooklyn, entering his plea. He spoke calmly in fluent English with a US accent, dressed in a dark suit.
As part of Monday's plea, he has agreed to forfeit USD 650,000: USD 180,000 to be paid within one week and the balance due within 12 months, prosecutors said during the 25-minute hearing.