Thousands of Orthodox Jews have defied a government ban to begin marching in protest at Israel's pullout from Gaza.
Organisers urged supporters to join the march any way they could
A massive security operation involving 20,000 police and troops is under way to prevent them from entering Gaza to disrupt next month's withdrawal.
After a two-hour stand-off with police, protesters agreed to halt for the night after walking 3km (2 miles).
But they have vowed to resume their three-day march despite the protest being declared illegal.
The demonstrators were spending the night in a floodlit campsite in Kfar Maimon, a village 3km from the Israeli town of Netivot, their starting point, about 23km east of Gaza.
They said they would push on towards the Gush Katif settlement bloc, via the Kissufim border crossing, in the morning.
Negotiations were set to continue during the night between police and protest leaders. The authorities have insisted they will not let the march reach Gaza.
The police had initially said they would not let the march go ahead at all.
Road blocks were set up, security forces lined the streets of Netivot and bus-loads of protesters were turned away.
Deputy Prime Minister Ehud Olmert warned that those who disobeyed the protest ban would be responsible for any trouble that might take place.
He said the plan to withdraw 21 Jewish settlements from Gaza had been approved by parliament and the demonstrators were trying to interfere with a legitimate decision of the Israeli government. The pull-out is supported by most Israelis.
Police superintendent Carla Oz told AFP news agency: "The rally is illegal. They did not receive a permit for this demonstration because their intention is to disturb the peace, so if large numbers of people come here they will be stopped."
The Israeli army has sealed off Gaza from all non-resident Israelis since Thursday night.
"We will try to get to Kissufim by every means possible without resorting to violence and to join our brethren in Gush Katif, who are under blockade," Emilie Amroussi, a spokeswoman for the main settler lobby, told AFP.
BBC Jerusalem correspondent Matthew Price says police moved aside to let the protesters past after initially blocking their way in Netivot.
There were minor scuffles, he reports, but on the whole, the protest was peaceful.
He says the Israeli government's nightmare scenario is that more settlers will join the 8,500 already living in Gaza.
That could make the withdrawal of Israelis from Gaza even more problematic than it already is, he adds.
The settlers and the soldiers that protect them are due to be withdrawn from Gaza, beginning in August. Israel will maintain control over Gaza's borders, coastline and airspace.
About 630 settlers will also be removed from four small West Bank settlements.
Israel has occupied Gaza and the West Bank since 1967.
Police arrested two soldiers on Monday, suspected of planting a fake bomb in Jerusalem's central bus station last week in protest at the disengagement.
The fake device was left with a note that said: "This disengagement will blow up in your face."