The West Bank barrier has been highly controversial ever since the Israeli government decided to build it in 2002 and it remains a bitter bone of contention after Israel's evacuation of settlements in the Gaza Strip.
The BBC News website answers questions about the plan.
Wall? Fence? What exactly is this structure?
"The Thing", as one commentator has drolly called it, is in fact part-wall, part-fence. Most of its 670-kilometre (420-mile) length is made up of a concrete base with a five-metre-high wire-and-mesh superstructure. Rolls of razor wire and a four-metre-deep ditch are placed on one side. In addition, the structure is fitted with electronic sensors and has an earth-covered "trace road" beside it where footprints of anyone crossing can be seen.
Parts of the structure consist of an eight-metre-high solid concrete wall, complete with massive watchtowers. The solid section around the Palestinian town of Qalqilya is conceived as a "sniper wall" to prevent gun attacks against Israeli motorists on the nearby Trans-Israel Highway.
There are also sections of wall around Jerusalem - blocking off Ramallah and Bethlehem and running through the village of Abu Dis.
Work started - at a cost of $2m a kilometre - in June 2002 and contractors have now completed about half of the planned barrier: a long segment on the north-west edge of the West Bank; two sections either side of Jerusalem; and a section in the Jordan Valley.
But construction has been slowed with the Israelis announcing some changes to the route necessitated by legal rulings.
On 20 February 2005 - the same day it approved the Gaza disengagement plan - Israel's cabinet approved the current planned route for the barrier, after Israel's Supreme Court ruled the previous route was needlessly disruptive to Palestinians' lives.
The new route runs closer to Israel's boundary with the West Bank - the Green Line - than the original one but will still include 6-8% of occupied territory in the West Bank on the Israeli side.
Why is Israel building it?
The government says it is essential to prevent Palestinian would-be suicide bombers from entering Israel and attacking Israeli civilians, as has happened many times during the Palestinian intifada.
Prime Minister Ariel Sharon's government was originally reluctant to build the barrier - which was first championed by the centre-left opposition Labour party.
Right-wing ministers and their hardline supporters were not keen to build any structure which might be construed as a future Israeli-Palestinian border which left Jewish settlements stranded in Palestinian land.
Pro-settlement objections have been largely assuaged by the fact that the structure is not being built on Israel's pre-1967 boundary, but snakes several kilometres into the West Bank to link settlements with Israel.
What are the main objections to the plan?
Israel's critics say the plan epitomises everything that is wrong with Israel's occupation of Palestinian land and its approach to making peace with its Arab neighbours.
Palestinian land is confiscated to build the barrier; hundreds of Palestinian farmers and traders are cut off from their land and means of economic survival. Most significantly, it creates "facts on the ground" and imposes unilateral solutions which preclude negotiated agreements in the future.
The impact of the plan has been felt acutely in Qalqilya, once known as the West Bank's "fruit basket", which lies within a tight loop in the wall. It is cut off on three sides - from the farms which supply its markets and the region's second-largest water sources. Access to the 40,000-inhabitant town passes through a single Israeli checkpoint.
Why didn't Israel build the barrier along the old 1967 boundary?
Palestinians say a fence around the entire West Bank might have shown the Israeli government was serious about ending the occupation - the minimum requirement for a fair resolution of the conflict as far as Palestinians are concerned.
As it is, the Palestinians argue, the current plan looks suspiciously like the precursor to a structure which will hem them into discontiguous "bantustans" on 42% of the West Bank - something they believe Mr Sharon has been planning all along.
But Israel argues that the fence is purely a security obstacle, definitely not a part of a future border. Israeli officials say there is nothing to prevent the fence from being moved after a negotiated settlement.
Can legal action stand in the way of the barrier?
Court challenges have been made to the barrier both internationally and in Israel itself.
The International Court of Justice ruled against the barrier in July 2004, saying that it breaches international law and should be dismantled. Calling it "tantamount to de facto annexation", the Court said the barrier inhibited Palestinians' right to self-determination.
The court's decision - which came at the request of the United Nations General Assembly - is advisory, not binding, and it has been rejected by the Israeli government.
Civil rights groups have meanwhile gone to Israel's Supreme Court questioning the principle of building the barrier on occupied land and the restrictions it imposes on the Palestinians in the West Bank.
This challenge has not succeeded, but more limited challenges have. In June 2004 the Court ruled that a 30-km section of barrier northwest of Jerusalem imposed undue hardship on Palestinians and must be rerouted.
The Supreme Court specifically said Israel had to limit Palestinian suffering, even if that meant accepting some restrictions on its ability to defend itself. It accepted that security was the reason for building the barrier.
A second ruling in September 2005 ordered reconsideration of the route around Alfei Menashe, south of Qalqilya, where several Palestinian villages have been left stranded on the western, "Israeli" side of the fence, devastating the local economy.
On this occasion, the court also rejected the World Court ruling, saying Israel did have the right to build the barrier on occupied West Bank land, but ordering that the route be determined by the army on the basis of security needs.
Where does America stand?
Washington, still keen to keep alive the roadmap peace plan, views the barrier as problematic because of its capacity to poison the atmosphere between the two sides.
In an exchange of letters in April 2004, President George W Bush outlined US policy in this way:
"As the government of Israel has stated, the barrier being erected by Israel should be a security rather than political barrier, should be temporary rather than permanent and therefore not prejudice any final status issues including final borders, and its route should take into account, consistent with security needs, its impact on Palestinians not engaged in terrorist activities."
What is the UN's position on the barrier?
In late September 2003, the UN issued a report which condemned the barrier as illegal and tantamount to "an unlawful act of annexation".
In his report for the UN Commission on Human Rights, John Dugard, a South African law professor, warned that about 210,000 Palestinians living in the area between the wall and Israel would be cut off from social services, schools and places of work.
"This is likely to lead to a new generation of refugees or internally displaced people," he said.
Israel has dismissed the UN report as "one-sided, highly politicised and biased".