Israel has freed 57 Palestinian prisoners from the West Bank in an attempt to bolster President Mahmoud Abbas against his rival Hamas ahead of peace talks.
But the release of a further 29 prisoners, headed for Gaza, has been delayed after the Israeli President Shimon Peres did not sign their pardons.
It was not clear why Peres, a strong advocate of peacemaking with the Palestinians, failed to sign them.
Israeli Prime Minister Ehud Olmert and Abbas will meet on Wednesday ahead of November’s US-sponsored conference on Palestinian statehood.
There are some 11,000 Palestinian men and women behind bars in Israel. All of those released on Monday had been detained for for attacks which did not kill Israelis.