A convicted drug smuggler has told U.S. investigators that he delivered a briefcase with $300,000 in cash to the office of Panamanian strongman Gen. Manuel Antonio Noriega to obtain Noriega's help in laundering millions of dollars in drug profits through Panamanian banks, according to informed sources.

Steven Michael Kalish, one of the Justice Department's chief witnesses in an ongoing criminal investigation of Noriega, has alleged to investigators that he left the money in Noriega's office in September 1983 when he was introduced to the general through two middlemen, sources said.

Kalish, who is scheduled to testify before a Senate subcommittee today, said that he was instructed to bring the cash to demonstrate that he was making a serious request for Noriega's help in connection with Kalish's multimillion-dollar drug smuggling operation, sources said.

New allegations about Noriega's involvement in drug smuggling are emerging as federal and congressional officials continue to press their investigations of Noriega, commander of Panama's armed forces and the country's de facto ruler. Federal grand juries in Tampa and Miami have been conducting criminal investigations of Noriega. Sources said yesterday that the Miami investigation is reaching its final stages.

The Reagan administration is pushing for Noriega to voluntarily step down and permit free elections and a transition to a full democracy in Panama.

Another person who has come forward claiming he can provide evidence tying Noriega to drug trafficking is Jose I. Blandon, the Panamanian consul general in New York, whom Noriega fired two weeks ago. Blandon has told congressional aides he has evidence of Noriega's involvement in arms trafficking and corruption in Panama.

Blandon has played a leading role in an effort to negotiate, initially with Noriega's blessing, a political solution intended to allow for a transition within a year to a full civilian government and Noriega's retirement in April. However, Noriega abruptly ordered Blandon to halt his efforts late last month.

Noriega, who headed Panama's military intelligence service for 13 years before becoming armed forces chief in 1983, has managed to withstand repeated challenges. Current and former U.S. officials said Noriega owes his survival in part to his longstanding relationship with the Central Intelligence Agency.

Noriega was on the CIA payroll for many years, according to current and former U.S. officials, and during the tenure of the late CIA director William J. Casey, he had a close relationship with the agency.

However, sources said, new CIA Director William H. Webster has questioned the agency's relationship with Noriega. Sources said Webster is concerned that the CIA lost control of Noriega. For example, Noriega has also maintained ties with Cuban intelligence and played the CIA and Cubans against each other, sources said.

In an interview last week, Washington lobbyist Thomas Hale Boggs Jr. said that in a conversation he had with Noriega nearly a year ago, Noriega complained that his relations with the CIA deteriorated after Casey left. "He certainly said he had very close ties with Casey," Boggs said. "He was very concerned that the new people there {at the CIA} did not know what his past contributions were."

In the early years of the administration's secret war against Nicaragua's Sandinista government, Noriega permitted the CIA-backed contras to train in Panama, sources said.

Blandon, who headed political counterintelligence for Noriega, has told congressional aides that he attended two or three meetings between Noriega and Lt. Col. Oliver L. North, then a National Security Council aide, in which other possible Panamanian support for the contras was discussed. Those meetings occurred when a congressional ban on U.S. government aid to the contras was in effect.

Noriega has repeatedly denied any role in drug trafficking and has charged that the recent allegations are part of a U.S. government campaign against him.

Current and former U.S. officials have said that while rumors of Noriega's alleged drug involvement have existed for more than 15 years, the evidence has often been hearsay of questionable credibility. Frequently the witnesses are convicted criminals seeking leniency.

Through an aide yesterday, Sen. William V. Roth Jr. (R-Del.), who will preside over today's hearing of the Senate Governmental Affairs permanent subcommittee on investigations, said that Kalish's allegations "describe Gen. Noriega as not just aware but as a central agent in drug trafficking and money laundering in Panama."

Federal prosecutors in Tampa have said that Kalish was a key member of a drug ring that arranged the importation of more than 500,000 pounds of marijuana and 3,000 pounds of cocaine into the United States between June 1982 and October 1985. Kalish, serving an eight-year sentence on previous drug-related charges, awaits sentencing in the Tampa case.

Kalish has told federal investigators that as the millions in cash from his drug operation accumulated, he began laundering funds through Panama, which has strict bank secrecy laws, sources said. Kalish said he met Noriega through two Noriega associates, including Cesar Rodriguez Contreras, a suspected drug pilot murdered in Colombia in 1986.

Kalish has told congressional aides that as part of a scheme to allegedly channel payoffs to Noriega he purchased an interest in a company in which Noriega was a hidden partner, sources said.

Congressional and federal investigators have heard allegations from Kalish, Blandon and others that Noriega also allegedly has aided a group of Colombian drug kings, known as the Medellin cartel, which U.S. officials believe is responsible for most of the cocaine smuggled into the United States.

A former Noriega pilot, Floyd Carlton Caceres, has told federal investigators that he was a conduit for alleged payoffs to Noriega from the Medellin cartel, sources said.

Carlton began cooperating in the Miami probe after his conviction on drug charges. He is scheduled to testify before a Senate Foreign Relations panel next month.