The Palestinians challenged Israel on Monday to accept the world court's ruling and destroy the barrier it is building to seal off the West Bank (search), warning that failure to do so will lead to "practical measures" against its construction.

Nasser Al-Kidwa, the Palestinian U.N. observer, said he wouldn't specify the measures the Palestinians will seek against the barrier.

Following Friday's opinion by the International Court of Justice, Israeli Prime Minister Ariel Sharon (search) on Sunday ordered construction of the barrier to continue and vowed "to fight using all diplomatic and legal means" against the court's decision.

Al-Kidwa expressed hope that Israel will recognize that the ruling offers a chance to end the current "quagmire" in the Israeli-Palestinian conflict (search) and move toward a negotiated comprehensive peace based on the rule of law and a two-state solution along pre-1967 borders.

"Frankly, we remain hopeful in spite of the hysteric initial reactions by some Israeli quarters, and frankly my advice to some of them ... is to be careful," Al-Kidwa told a news conference.

"The bottom line is this. If Israel does not comply with its obligations as determined in the advisory opinion, it will become officially, judicially, an outlaw," he warned.

Al-Kidwa argued that even though the ruling is an advisory opinion, "the court spoke of legal obligations of Israel" to stop construction, dismantle the barrier, and provide reparations to Palestinians whose lives have been harmed by it.

While Al-Kidwa maintained that "the advisory opinion has the strength of the law," Israel's U.N. Ambassador Dan Gillerman has argued that it is not legally binding and he insisted it was erected purely as a temporary measure to protect Israelis against homicide bombers and other attacks.

At the Palestinians' request, the U.N. General Assembly asked the world court in December for an opinion on the legality of the barrier — a 425-mile-long complex of walls, razor-wire fences, trenches and watch towers. Much of the completed portion is close to Israel's pre-1967 border, but some of it dips into the West Bank.

In its sharply worded opinion, the court not only called for the barrier to be torn down but urged the General Assembly and the Security Council to consider "what further action is required to bring to an end to the illegal situation."

Arab nations supporting the Palestinians met Monday morning to consider the next steps. Al-Kidwa told a news conference afterward that they would first seek a General Assembly resolution demanding compliance with the court ruling and asking the U.N. Secretariat to help determine compensation for those harmed by the barrier.

The 191-nation world body can recommend that the wall be torn down, and it can recommend sanctions or other measures if Israel fails to comply. But only the 15-member Security Council can order such actions.

Al-Kidwa said the additional measures the Palestinians might take "are not necessarily a sanctions regime against Israel."

"There are many things you can take in practical measures, especially against the actual process of the construction of the wall, and also against other illegal activities in the occupied territories, especially settlement activities," he said.

The United States, Israel's closest ally, has blocked many Security Council resolutions, but Al-Kidwa said Washington should deal with the court's opinion "in a respectable way."