Brothers Gilberto and Miguel Rodriguez Orejuela made billions of dollars building Colombia's Cali cartel into the world's top supplier of cocaine during the 1990s. Now, they are likely to spend their elder years in a U.S. prison.

Gilberto, 67, and Miguel, 62, were expected to plead guilty in federal court Tuesday to drug charges in an agreement reached after months of negotiations with several U.S. agencies.

The deal is intended to protect six relatives in Colombia from prosecution on obstruction of justice and money laundering charges, according to federal law enforcement officials and attorneys familiar with the negotiations. They spoke on condition of anonymity Friday because the agreement was not complete.

The deal could permit a total of 28 people with ties to the brothers, including the six relatives, to keep property and other assets not tainted by drug money. The 28 could eventually be removed from a U.S. list freezing their assets and blocking them from doing business with U.S. entities, the officials have said.

The brothers could face sentences that would effectively keep them behind bars in the United States for the rest of their lives.

The Cali cartel became the world's leading cocaine smuggling ring after eclipsing the rival Medellin cartel, which fell apart when several top members were arrested and Medellin top kingpin Pablo Escobar was killed in a 1993 shootout with Colombian police.

The Cali cartel was once responsible for as much as 80 percent of the cocaine smuggled into the United States. It was known for its ingenious smuggling methods that hid cocaine in such things as hollowed-out lumber and cylinders of chlorine, even shipments of frozen broccoli and okra.

U.S. prosecutors were seeking forfeiture of about $2.1 billion in drug profits from the brothers, who probably made many times that amount during the cartel's heyday. William Rodriguez Abadia, Miguel's son and Gilberto's nephew, agreed to forfeit about $300 million in worldwide assets after pleading guilty in March to U.S. charges and agreeing to testify against his father and uncle.

The Rodriguez Orejuela brothers were convicted in Colombia of drug charges in 1995, but were indicted in 2003 in Miami on charges that they continued to run their cocaine empire from behind bars. Gilberto Rodriguez Orejuela was extradited in late 2004 and Miguel Rodriguez Orejuela in early 2005. They were the highest-ranking of more than 300 drug traffickers extradited since the U.S. and Colombia signed a new treaty in 1997.

All told, the Cali cartel is estimated to have smuggled more than 250 tons of cocaine into the United States since the 1970s. A recent DEA analysis said that several Colombian organizations now control that country's cocaine trade, increasingly in concert with Mexican organizations that distribute the drug in the United States.