Israel's Supreme Court has backed a prisoner swap with Hamas, rejecting petitions against freeing more than 1,000 Palestinian prisoners in exchange for captured soldier Gilad Shalit.
Families of victims of attacks by militants wanted a 48-hour delay on the swap, which is due to begin on Tuesday.
The court had allowed Sgt Shalit's parents to argue in favour of the deal.
They have cautioned against any delay, saying it could endanger the terms of their son's release.
"Nobody knows what the impact of any delay, or any change, even the smallest, in the terms would be," they wrote in a letter to the court.
The court ruled that the decision to exchange prisoners rested with the government, Israeli military radio reported. Correspondents said the court was always unlikely to intervene in what it considers a political and security issue.
On Sunday, Israel published the names of 477 Palestinian prisoners due to be released on Tuesday in the first phase of the deal.
A further 550 prisoners are to be released after Sgt Shalit returns home.
The Supreme Court heard four petitions filed by the Almagor Terror Victims' Association and relatives of Israelis killed in Palestinian attacks. They said more time was needed to review all the names on the prisoner list.
"I understand the difficulty in accepting that the vile people who committed the heinous crimes against your loved ones will not pay the full price they deserve," Prime Minister Benjamin Netanyahu wrote in a letter to bereaved Israeli families.
Israeli President Shimon Peres has also urged support for the families.
"Friends and colleagues, let us all embrace the families who lost their loved ones in the war of terror, who carry a grief they cannot escape and still continue to love their nation with dignity and nobility," he said.
A recent opinion poll in the Israeli newspaper Yedioth Ahronoth found that 79% of the public supported the deal, agreed last week by Israel and the militant Palestinian Islamist group Hamas.
Hamas is preparing a hero's welcome in the Gaza Strip in anticipation of the release of the prisoners.
Earlier, Ron Kehrmann, whose daughter was one of 17 people killed in a 2003 bus suicide bombing in Haifa, said he was asking the Supreme Court to stop the release of three Palestinians linked to the attack.
However, he told Israeli Army Radio he was not hopeful, adding: "This whole fiasco - it's fixed."
Israel has already transferred the 477 Palestinians to two holding facilities. On Tuesday, some will be taken to Egypt's Sinai desert where the exchange for Sgt Shalit will take place.
The second stage of the deal is expected to happen in about two months, correspondents say.
Sgt Shalit was snatched in 2006, aged 19, in a cross-border raid by Hamas militants who tunnelled from Gaza into Israel.