A one-time confidant and business partner of Manuel Antonio Noriega pleaded guilty to two drug charges yesterday as part of a plea agreement in which he has agreed to testify against the deposed Panamanian dictator, federal prosecutors said.

Enrique "Kiki" Pretelt, a Panamanian businessman arrested by the Federal Bureau of Investigation earlier this year, entered a two-count felony plea in federal court in Tampa. He admitted to conspiring with Noriega and convicted drug smuggler Steven Kalish to form a business to launder drug profits and import 400,000 pounds of Colombian marijuana to the United States via Panama in 1983 and 1984.

The government's agreement with Pretelt represents a potentially damaging blow to Noriega given the longtime business and person- al relationship between the two

men.

It also came while U.S. Judge William Hoeveler, in a separate and larger cocaine trafficking case in Miami, rejected Noriega's motion that, as a head of state, he was immune from any alleged criminal activities.

Hoeveler also rejected defense motions that Noriega should be freed on the grounds that the invasion of Panama that led to his arrest should "shock the conscience" of the court. "Noriega's complaint is a challenge to the very morality of war itself," wrote Hoeveler in an 80-page opinion. "This is a political question."

In February 1988, while he was still Panama's leader, Noriega was indicted on drug-trafficking charges by two federal grand juries, one in Miami and another in Tampa. As part of Pretelt's plea in the Tampa case, he has agreed to testify that Noriega conspired with Kalish and the late Cesar Rodriguez to ship marijuana from Colombia in containers labeled as containing plantains and then relabel the containers in Panama as being of Panamanian origin.

Noriega's trial in the Tampa marijuana case has been deferred until the completion of the larger cocaine trafficking case in Miami. Although Pretelt was not mentioned in the Miami indictment, his lawyer, George Tragos, said yesterday that Pretelt also was prepared to testify against Noriega in that case and possessed information that would be "helpful" to the government.

Pretelt was with Noriega in Havana in June 1984 when the Panamanian strongman met with Cuban dictator Fidel Castro and, according to the Miami indictment, discussed a dispute between Noriega and Colombia's Medellin drug cartel, Tragos said.

"The government is desperate to obtain whatever witnesses it can to shore up its case," said Jon May, one of Noriega's defense lawyers, when asked about Pretelt's plea. He said numerous accused drug traffickers were being offered "wonderful deals" in exchange for their testimony against Noriega but "that doesn't necessarily mean they are telling the truth."

A wealthy jeweler who also ran a string of duty-free shops in Panama, Pretelt was "close personal friends" with Noriega and a partner in a number of business ventures, Tragos said. As part of the plea agreement, Pretelt has agreed to forfeit $108,000 -- his share of the profits from the marijuana-smuggling attempt. In exchange, the government has agreed that he will receive a sentence of no more than 10 years and that he will not be prosecuted for any further crimes he may reveal as a result of his cooperation with the government. Prosecutors also have agreed to recommend to the Immigration and Naturalization Service that Pretelt not be deported to Panama if the new Panamanian government attempts to prosecute him.

The deal offered by the government "was so good, we couldn't really turn it down," said Tragos, particularly "when you consider his liability all over the place."