NEW YORK (AFP) - Drug baron Joaquin "El Chapo" Guzman paid huge bribes to Mexican prosecutors, police, military and even Interpol to ensure smooth operations for his Sinaloa cartel, a key informant said at his US trial on Thursday (Nov 15).

Jesus "El Rey" Zambada, brother of the cartel's co-head, the still-at-large Ismael "El Mayo" Zambada, detailed the eye-watering costs of protecting cocaine shipments that originated in Colombia and traveled to the US via Mexico - with payments amounting to US$300,000 (S$400,000) a month in Mexico City alone.

Zambada, who worked for the cartel from 1987 until his arrest in 2008, was returning to the witness stand on the third day of a trial expected to last about four months.

He told the court that as the head of the organisation's operations in the capital city, he personally paid bribes to the attorney-general's office, the federal highway police that also operates bridges and airports, federal, state and local police forces, and "Interpol, as well."

"The bribes for officials in Mexico City were about US$300,000 per month," the 57-year-old said, wearing a blue prison suit with an orange shirt.

Zambada added he once paid a US$100,000 bribe to General Gilberto Toledano, in charge of the state of Guerrero, at Guzman's request.

"I was going to import cocaine from Colombia through the state of Guerrero... and El Chapo told me 'Go and meet General Toledano, he's my friend, and give him $100,000 from me,'" Zambada said.

Guzman, wearing a dark suit and tie, listened attentively to the testimony of his former ally.

Brought to the US almost 22 months ago, Guzman, 61, is accused of smuggling more than 155 tons of cocaine into the United States over 25 years and faces life in prison if found guilty.

His lawyers argue he has been scapegoated by Mexico's "corrupt" government and the US Drug Enforcement Agency, and that the cartel's true chief was Ismael Zambada.