Apple chief executive Tim Cook and top Samsung executives failed to agree on patent values during settlement talks.
Apple and Samsung, the world's largest consumer electronics corporations, are waging legal war in several countries, accusing each other of patent violations as they vie for supremacy in the fast-growing market for mobile devices.
The trial is scheduled to begin next week in a San Jose, California federal court.
Cook participated in mediation with Samsung's Vice Chairman Choi Gee-sung and mobile chief Shin Jong-Kyun last week in the San Francisco area to see if the two sides could resolve the dispute, several separate sources said.
All sources could not be identified because they were not authorized to speak publicly.
The executives from Apple and Samsung participated as part of the court directed mediation process, these sources said.
While a settlement is always possible, it is unlikely to come ahead of the California trial, they said.
Apple has declined to comment on the case, while a Samsung spokesman declined to provide details on any discussions, saying "this is an ongoing legal matter".
The U.S. case, taking place a few miles away from Apple's headquarters in Cupertino, California, is being closely-watched given the lucrative American smartphone and tablet market.
Among the major issues in dispute between Apple and Samsung is how to value so-called standard essential patents.
These are patents which Samsung agreed to license to competitors on fair and reasonable terms, in exchange for having the technology be adopted as an industry standard.
Some judges are reluctant to issue injunctions over such patents.
Apple believes those patents should be valued lower due to those dynamics, one of the sources said.
Additionally, Samsung believes it has a stronger patent portfolio than Apple when it comes to next-generation technology like 4G, the source said.
The mediation last week was at least the second between top executives.
A previous session in May did not produce any settlements.