Israel's plan to free 230 Palestinian prisoners on Monday morning was thrown into doubt late Sunday night, after the country's Supreme Court ordered the release delayed until the state replied to a petition against it, dpa reported.
Israeli media reported that Supreme Court Justice Eliakim Rubistein ordered the state to reply by 7:45 am (0545 GMT) to the petition, and said only after hearing the state's arguments would a final ruling on the appeal be made.
The transfer of the prisoners to the Palestinian areas would not go ahead before then, Rubinstein said.
The court had earlier rejected the petition, saying that the release was a political decision affecting Israel's foreign relations, and thus outside its competence.
The petitioners, however appealed the ruling, prompting Rubinstein to order the release delayed until the state responded to the petition.
Israel decided to free the 230 prisoners as a goodwill gesture to Palestinian President Mahmoud Abbas, to mark the Muslim festival of Eid al-Adha (Feast of the Sacrifice.)
All the prisoners to be freed are members of the armed wings of Abbas' secular Fatah movement, or other smaller groups, and none of the radical Islamic Hamas movement.
Israel has said the periodic release of small numbers of Fatah militants is aimed at boosting support for the moderate Palestinian president in his power struggle with his bitter rival Hamas.
The release was supposed to have taken place last week, but was postponed. Israel said the delay was due to a request from the Palestinians, but Palestinian officials denied this.