Jordan has criticised Israel for its construction of the West Bank barrier on the second day of hearings at the International Court of Justice (ICJ).
The issue is also a battle for public opinion
Israel's neighbour said it feared the barrier would create an exodus of refugees which would strain the country's resources.
But Israel pressed ahead, starting work on a new section of the barrier.
Israel says the barrier keeps suicide bombers out of the Jewish state, but Palestinians say it is a land grab.
The head of the Jordanian delegation, Prince Zeid Bin Raad, told the court that his country would suffer the most from the barrier.
"My country already hosts a huge number of refugees and displaced persons," Prince Zeid Bin Raad was quoted by AFP news agency as saying.
"We are faced with the threat of a new wave of refugees as a result of the wall's construction."
However, another row between the countries was averted when Israel withdrew its threat to force all Jordanians living in the West Bank to apply for Palestinian passports.
Jordan feared that might have persuaded nearly 200,000 people to seek refuge in their country rather than register as Palestinian.
Meanwhile, Belize told the court in The Hague that the human rights of Palestinians were being abused by the barrier, although it said Israel did have the right to defend itself.
Cuba described the barrier's construction as a potential humanitarian catastrophe which would create a "population of prisoners", Reuters news agency reported.
Indonesia, the world's most populous Muslim nation, also called on the court to declare the barrier illegal.
The United Nations General Assembly asked the International Court of Justice to consider the barrier issue.
Fourteen countries and organisations, mostly sympathetic to the Palestinian argument, are speaking over three days.
KEY PLAYERS' POSITIONS
Palestinians: Barrier a violation of rights; crosses into occupied land, therefore illegal
Israel: Barrier vital for security, no political significance; ICJ has no jurisdiction; hearing could undermine peace moves
US: ICJ has no place in dispute; road map is way forward
EU: Against barrier crossing into West Bank; ICJ hearing divisive, inappropriate
44 UN members submitted arguments to court
Speaking for Palestinian case: 14 countries and organisations including South Africa, Arab League
The court ruling - if one is made - is not expected for several months and will not be binding. However, correspondents say it would have great symbolic importance.
Israel struck a defiant note on Tuesday by starting work on a 42km stretch of the barrier in the northern West Bank village of Beit Surik.
Clashes broke out when around 100 villagers tried to stop two Israeli bulldozers from levelling a field of olive trees, by lying down in their path.
Israel itself is not taking part in the barrier hearings, disputing the right of the World Court to rule on what it sees as a political dispute with the Palestinians, not a legal one.
Israelis launched their own protest up the road from The Hague, staging a mock hearing which concluded that their country "has an absolute right to defend itself".
Arnold Roth, whose 15-year-old daughter, Malka, was killed in an attack on a Jerusalem pizza restaurant in 2001, said: "The fact that these death cult murderers are able to carry out their disgraceful, disgusting acts is what brings us all here."
On Tuesday Israeli Prime Minister Ariel Sharon denounced the hearing as an "international circus" and vowed to complete construction of the barrier.