Palestinian Prime Minister Ahmed Qurei has called for an urgent international meeting to discuss the barrier Israel is building in the West Bank.
Mr Qurei is seeking to drum up support in Europe
Speaking in Ireland at the start of a European tour, he urged the "quartet" of peace sponsors - the EU, UN, US and Russia - to meet as soon as possible.
Mr Qurei said the barrier threatened a key aim of the peace "roadmap" - to create a separate Palestinian state.
Israel's Supreme Court has begun hearing a case against the barrier.
The case was brought by two Israeli human rights groups, who argued that sections of the barrier had been built illegally on occupied territory and therefore should be re-routed along Israel's border with the West Bank.
A lawyer for the Israeli Government replied that the challenges to the barrier were too general and should be dismissed.
The hearing comes two weeks before the International Court of Justice is due to consider if the barrier contravenes international law.
Israel says the 720-kilometre (480-mile) barrier is necessary to keep suicide bombers out. Palestinians say it is an attempt to grab land.
"It is time for the quartet to move," Mr Qurei told reporters at a news conference in Dublin, after talks with Irish Prime Minister Bertie Ahern, whose country currently holds the presidency of the European Union.
Mr Qurei urged the four to make a "very strong intervention, very serious action and immediately to stop it".
"It will kill the choice of two states," he added.
Mr Ahern said the talks had been highly useful and he would be discussing the situation in the Middle East at a meeting with US President George W Bush next month.
He said Mr Qurei pledged that "the Palestinian leadership would shortly make an unequivocal statement reaffirming their stated position on Israel's right to exist in peace and security and calling for an immediate end to violence."
On Monday, the two Israeli human rights groups - Hamoked and the Association for Civil Rights in Israel - presented their cases against the Israeli barrier.
"There's no doubting that Israel has the right to defend itself and build a barrier... but it is another thing to build it inside the occupied territories," Hamoked's lawyer Avner Pinchuk said.
Israeli Government lawyer Michael Blass replied that the challenges to the barrier were too general.
Mr Blass also said the government was considering altering the route of the barrier.
Israeli officials had said a day earlier that the route could be shortened by about 100 km (62 miles), and plans to loop it around Jewish settlements are expected to be dropped.
The government is also reportedly considering painting sections of the barrier to make it less ugly.
A three-judge panel spent about two hours listening to arguments. They are expected to rule in the next few days, according to justice ministry sources cited by the AFP news agency.
If the court rules in favour of the petition, correspondents say a lengthy legal process could follow.