Jury selection was scheduled to begin on Wednesday for the federal trial of Abu Agila Mohammad Mas'ud Kheir Al-Marimi in Washington DC. His trial will be the first in the United States for the December 21, 1988, bombing over Lockerbie, Scotland, which killed 270 people, most of them Americans.
US District Judge Dabney Friedrich's order on Monday didn't specify the nature of the newly discovered evidence.
Al-Marimi's lawyers say prosecutors disclosed the new evidence to them on Saturday and added their "constitutional and ethical obligations require the defence to investigate this development".
Defence lawyer Laura Koenig, an assistant federal public defender, declined to elaborate in response to an Associated Press inquiry.
The judge scheduled a September 1 hearing in Washington to discuss the status of the case. Friedrich's brief order cited the complex nature of the case, the newly discovered evidence and "the need for the defence to determine how best to defend this case" as reasons to postpone the trial.
Al-Marimi is charged in the US with making the bomb that downed the plane.
Flight 103 was 31,000 feet over Lockerbie when a bomb in the plane's forward cargo area exploded 38 minutes after takeoff from London Heathrow Airport. The flight was bound for John F Kennedy International Airport in New York.
The blast killed all 259 passengers and crew members and 11 people on the ground in Lockerbie, where the wreckage destroyed an entire city block.
Citizens of 21 countries were killed, including 190 Americans and 43 from the United Kingdom.
Prosecutors allege Al-Marimi and others carried out the bombing at the direction of Libyan leader Moammar Gadhafi, who was ousted and killed during a 2011 civil war.
Two other Libyan intelligence agents were tried by a panel of Scottish judges on a former US military base in the Netherlands in 2000. The tribunal convicted one official and acquitted the other, but the bombmaker's possible identity remained a mystery for years.
Al-Marimi, now in his mid-70s, is charged with two counts of destruction of an aircraft resulting in death. He faces a maximum penalty of life in prison if convicted.
Al-Marimi worked for the Libyan intelligence service from approximately 1973 to 2011, rising to the rank of colonel, according to prosecutors.
Prosecutors believe he brought a suitcase containing a bomb to an airport in Malta and gave it to co-conspirators for a flight to Frankfurt, Germany. The suitcase travelled from Frankfurt to London, where it was loaded onto Flight 103, according to investigators.
