A Mexican federal judge on Thursday rejected an appeal by drug lord Joaquin "El Chapo" Guzman against his extradition to the United States.
The Mexican foreign ministry approved the extradition request in May, but Guzman's lawyers have been fighting the decision in a district court.
One of Guzman's lawyers, Andres Granados, vowed to seek a Supreme Court hearing.
"We are not defeated," Granados said, adding that he could still take the case to the Inter-American Commission on Human Rights.
The head of the Sinaloa drug cartel was recaptured in January after escaping for a second time from a maximum-security prison. He is currently imprisoned in the northern border state of Chihuahua.
Mexico has said it expects to extradite Guzman by February.
Guzman is facing two extradition bids, one in California for drug distribution and another in Texas on charges that include murder and money laundering.
His extradition would set up a major trial in the United States for the head of a cartel accused of providing tons of drugs to addicts in the United States while fueling violence in Mexico.