Federal prosecutors have filed papers accusing Rep. William J. Jefferson, D-La., of participating in two additional bribery schemes but do not plan any new charges.

The court papers, filed Friday in U.S. District Court in Alexandria, Va., by U.S. Attorney Chuck Rosenberg, says the additional information will be introduced at Jefferson’s trial to show a pattern of behavior that backs up the existing charges against him.

Jefferson was indicted June 4 on 16 charges, including soliciting bribes, racketeering, money laundering, obstruction of justice, wire fraud, conspiracy and violations of the Foreign Corrupt Practices Act, allegedly for attempts to influence a series of business ventures in Africa.

Federal prosecutors said Jefferson, a nine-term House member from New Orleans, solicited an unidentified rocket technology and commercial launch services company through a businessman to get commissions for a relative. In return, Jefferson promised in June 2005 to undertake official acts, including writing a letter to NASA, on the company’s behalf, the government said.

In July 2005, Jefferson, then head of the Congressional Black Caucus Foundation, wrote a letter on the foundation’s letterhead to NASA on the company’s behalf, the filing said, adding that Jefferson’s signature was accompanied by the notation “M.C.,” for member of Congress.

Jefferson also allegedly sought a $10,000-a-month retainer for another family member through an unnamed lobbyist and a company identified as an “established oil services company’’ that did business in Nigeria. It was Jefferson’s dealings in Nigeria that form the basis for the federal indictment, which came after a two-year investigation.

Prosecutors said Jefferson and the lobbyist visited Nigeria in January 2002, and the lobbyist later asked Jefferson to arrange meetings with high-ranking Nigerian officials and big private oil companies doing business in the west African nation to help promote the oil services company.

Jefferson agreed to the request but suggested that his relative be hired by the company as a $10,000-a-month consultant, the government said. It added that the lobbyist understood that in making that request Jefferson was soliciting a bribe that “would be concealed through the use of a retainer agreement.’’

The filing said the new allegations were “inextricably intertwined’’ with the evidence already laid out in the indictment. Two former Jefferson associates have already pleaded guilty to bribing him, and an FBI affidavit said agents found $90,000 in marked bills in Jefferson’s freezer during a 2005 raid on his home.

Robert Trout, a lawyer for Jefferson, declined to comment Monday.

Perhaps the most serious charge against Jefferson, who was forced to give up his seat on the House Ways and Means Committee, was that he tried to bribe a Nigerian official. That allegation marked the first time any U.S. official has been charged under the 1977 Foreign Corrupt Practices Act (PL 105-366), according to the U.S. Justice Department.

Jefferson’s criminal case has been complicated by a battle over the powers of the legislative and executive branches of government. That issue arose last year when the FBI raided the congressman’s Rayburn Building office. A federal judge ruled the raid was constitutional, dismissing a challenge from House leaders.

But in August, a three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit ruled that much of the material the FBI seized in the May 2006 raid was taken in violation of the Constitution’s Speech or Debate Clause. That clause was designed, in part, to protect legislative or privileged documents.

The court ordered much of the seized material returned to Jefferson. Earlier this month, the court turned aside the federal government’s appeal of the August ruling.

Kathleen Hunter contributed to this story.