Gen. Manuel Antonio Noriega, Panama's military commander and de facto ruler, was indicted yesterday on federal drug and racketeering charges that he used his vast governmental powers to convert Panama into a safe haven for international drug traffickers, according to U.S. law enforcement sources.

Noriega was charged in a sealed indictment returned by a federal grand jury in Miami, sources said. The Miami indictment is scheduled to be made public today.

A U.S. criminal indictment of an incumbent foreign leader is virtually unprecedented. A law enforcement official said yesterday that research by the Justice Department indicates that only one other sitting foreign leader, the chief minister of the Turks and Caicos Islands, a tiny British dependency in the West Indies, has ever been indicted by the United States.

Noriega's indictment is expected to have serious diplomatic and political ramifications that extend far beyond the specific criminal allegations.

The indictment coincides with a strong effort by the Reagan administration and Congress to pressure Noriega to resign, which has prompted Noriega and others to allege that the indictments are part of the campaign to oust him. The Panamanian constitution bars extradition of its citizens, making chances slim that Noriega will come to trial in the United States.

Federal prosecutors have also received approval to seek a separate indictment of Noriega in Tampa, Fla., and the U.S. attorney's office there has scheduled a news conference on the subject today.

Sources said the Miami indictment charged Noriega with violating federal racketeering and drug laws by participating in Panama in a criminal enterprise that included leaders of the notorious "Medellin cartel" group of Colombian drug kings. Investigators say the cartel is responsible for most of the cocaine smuggled into the United States.

Sources said the Tampa investigation is largely tied to allegations made by convicted drug smuggler Steven Michael Kalish, who told a Senate subcommittee last week that he made hundreds of thousands of dollars in payoffs to Noriega.

In the Miami indictment, sources said, Noriega is charged with playing a pivotal role in a conspiracy that shipped drugs through Panama to the United States and used Panamanian banks to launder millions of dollars in illicit profits from U.S. drug sales. Noriega is named in the indictment along with 15 other defendants, including drug smugglers, pilots and money launderers.

U.S. law enforcement officials deny that the charges are part of an administration attempt to force Noriega out, but some officials note that the new chill in official relations with Panama has made it easier to investigate Noriega.

Noriega, 51, who became Panama's military commander in 1983 after serving as chief of military intelligence, has repeatedly denied any involvement in drug trafficking. He has denounced the investigations as part of an effort by some U.S. officials to discredit Panama.

CBS News reported last night that Noriega in a television interview called the indictment "strictly a political act aimed at frightening me."

As a sign of the case's sensitivity, Attorney General Edwin Meese III took a "personal hand" in discussions at the Justice Department this week that led to the decision, and the impending charges were also discussed at the White House, according to an administration source.

The United States has major national security interests in Panama, site of the strategically important Panama Canal and the largest U.S. military base in Latin America.

Within the last seven months, the rise of the most sustained internal political opposition to Noriega and a worsening economic situation in Panama have prompted the Reagan administration to push for Noriega to resign.

U.S. policymakers believe that Noriega must depart before free elections and a civilian democratic government can occur in Panama.

Officials said the administration is wary about how Noriega and Panama will react to the indictment.

Current and former U.S. officials said that in the short run, the charges will likely make it more difficult for Noriega to resign and permit a smooth transition to a civilian government.

And, U.S. officials said, Noriega would be effectively blocked from moving to the United States or to a country where he could be extradited here.

Officials also said some policymakers fear the indictment might cause Noriega to expand his ties to Cuba's Fidel Castro and Nicaragua's Marxist Sandinista government. However, other officials said it is likely to add steam to the internal effort to oust Noriega.

William J. Jorden, a former U.S. ambassador to Panama, said yesterday that "in the short term {the indictment} will harden him. It will make it more difficult for him to step down gracefully. On the other hand, the pressures are likely to build up to a point where there is no other choice than for him to go."

Noriega has managed to withstand repeated challenges. Current and former U.S. officials said the United States in the past had not moved against Noriega in part because he had a longstanding relationship with the Central Intelligence Agency. For example, current and former officials said, during the tenure of the late CIA director William J. Casey, Noriega had close ties with the agency.

In recent years, Panama has received praise from top U.S. law enforcement officials, including Meese and John C. Lawn, director of the Drug Enforcement Administration (DEA), for its cooperation on drug investigations.

Officials said DEA is in a delicate situation because it played a leading role in the Miami investigation and its agents also are dependent on Panama for help in the war against drugs.

Allegations about Noriega's involvement in drugs have been around for 15 years. But law enforcement officials said that until recently the evidence has not been viewed by prosecutors as strong enough to take a case into court.

Sources said a major break occurred when a former top Noriega drug pilot, Floyd Carlton Careres, began cooperating with the DEA and the Miami U.S. attorney's office last year after his conviction on drug charges.

Carlton's information was later unexpectedly corroborated by Jose I. Blandon, a former top Noriega aide who recently became a leading Noriega critic, sources said.

Among the allegations cited by Blandon is that Noriega has close ties to Castro and that Noriega has played the CIA and Cubans against each other.

Blandon has said he was present at a meeting in Havana when Castro mediated a dispute between Noriega and leaders of the Medellin cocaine cartel.

Other sources said the meeting took place on June 29, 1984, and that Castro's role was expected to be briefly cited in the Miami indictment. No charges were filed against Castro.