SAN DIEGO (AP) _ A cocaine ring involving Mexican officials and believed capable of producing about half the drug consumed in the United States was broken up by luring seven key members here on the pretense of receiving a $1 million payment, authorities said Friday.

Twelve foreign nationals, including five Mexicans with past or present ties to the Mexican government, are accused of operating the cocaine ring, U.S Attorney Peter Nunez said in announcing the unsealing of a 15-count indictment and criminal complaint.

''The thrust of the investigation was to ... document the flow of narcotics from Bolivia through Central America to the United States,'' Nunez said. He said the charges were the result of a six-month undercover probe in which DEA agents posed as American drug traffickers.

Charles Hill, special agent in charge of the San Diego DEA office, said he believed the breakup of the cartel would at least put a dent in the amount of cocaine reaching the United States.

''This group had the capability of importing about 86 tons of cocaine into this country in a year's time,'' he said. ''The DEA estimates that the consumption of cocaine annually (in the United States) is about 150 tons.

''I'm by no means making the statement that we're cutting the supply in half,'' said Hill. ''(But) I'm very optimistic that you might see some sort of impact as a result of this case.''

Undercover agents for the DEA and U.S. Customs had traveled to Bolivia, Mexico and Panama during the course of the investigation and, said Hill, ''we've worked right to the very top level.''

Hill said the agents were negotiating a deal for five tons of cocaine that would have cost $25 million. The cocaine was to be flown from Bolivia to the United States via Mexico, where the former and current Mexican officials had promised to use their influence to protect the drug shipment, Hill and Nunez said.

A spokesman for the Mexico attorney general's office said some of those indicted had claimed falsely to be federal officials.

Hill said an initial $500,000 payment was made, followed by the promise of a $1 million down payment. That was what brought the seven people now in custody to San Diego.

Arrested were Efren Mendez-Duenas, 58, a Mexican citizen residing in Bolivia, and Jorge Roman-Salas, 50, a Bolivian citizen. The two were described by authorities as being the principal administrators and organizers of the drug enterprise.

Others arrested were Mario Vargas-Brunn, 28; Pablo Giron, 40; Hector Manuel Alvarez-Brumel, 47; Jorge Carranzas, 52, whom authorities said was a former Mexican army colonel; and Rolando Antonio Ayala, 27.

Among the five fugitives was a Mexican general identified as Poblano Silva and a former lieutenant colonel from Mexico, identified as Salvador De La Vega.

The complaint and the indictment accuses the 12 of conspiring to import cocaine and possess cocaine with intent to distribute.

Felipe Flores, a spokesman for the Mexican Attorney General's office, said Giron and Alvarez-Brumel had claimed to be Federal Judicial Police agents.

''This was checked and neither of them has ever belonged to the Federal Judicial Police or to the attorney general's office,'' he said.

''Mr. Carranza resigned from the army 18 years ago, in 1970,'' Flores said. He was a major and on retirement, as is customary, was raised a rank to lieutenant colonel, he said.

The attorney general's Office has seen only news reports about the others named in the indictment but has received no official notification from U.S. authorities, he said.

He said the office had asked both in the United States and through the U.S. Embassy here for information so it could investigate.