The Arab League and Organisation of the Islamic Conference (OIC) - representing more than 50 countries - on Wednesday raised their objections at the UN's top court to the line of fences, walls and trenches that cut into land where Palestinians seek a state.
The two organisations, which represent about 20% of the world's population and include some of Israel's fiercest foes, were the last to address the court in one of the most closely watched cases in its 58-year history.
"Does this not all bring back to the present the Berlin Wall episode which was dubbed the wall of shame?" Arab League representative Michael Bothe asked the court.
"The wall is profoundly affecting the living conditions in the Palestinian occupied territories. It leads to migration, to the displacement of major parts of the Palestinian population, to a consolidation of the unlawful Israeli settlements."
Israel says it needs the barrier to keep out Palestinian human bombers, who struck again on Sunday, killing eight.
Palestinians, who have asked the court to declare the so-called apartheid wall illegal, call it a land grab to deny them a viable state.
Israeli police clash with anti-wall
protesters in the West Bank
"With the wall there is no longer a viable Palestine thus no peace possible between the two states," said Monique Chemillier-Gendreau, legal adviser to the 57-member OIC before the hearing closed at the court's Peace Palace.
Israel has stayed away from the hearings, disputing the court's right to rule in the case.
But Israelis have joined the battle for world opinion outside the court, holding street rallies and a mock "hearing" with relatives of bombing victims.
Hundreds of Palestinian protesters chanting "Allahu Akbar," (God is Greatest) clashed with Israeli security forces on Wednesday near to where work begun on a new section of the barrier.
The case in the Hague has underlined the stalemate in peacemaking efforts after more than three years of violence.
Israeli troops carried out their biggest raid on Palestinian President Yasir Arafat's headquarters city for months on Wednesday, firing teargas and rubber bullets to drive back Palestinians throwing stones and petrol bombs in Ram Allah.
Arafat's Fatah movement will discuss whether to dismantle an armed wing behind human bombings on Israelis, Arafat's security adviser, Jibril al-Rajub, said on Wednesday.
The court's 15 judges are expected to issue their opinion within months. Their decision is non-binding, but it could influence world opinion and the Palestinians hope it could pave the way for international sanctions against Israel.
A dozen countries, including Jordan, Cuba, South Africa and Saudi Arabia, have added their voices to the Palestinian case, which opened the three-day hearing on Monday.