Israeli Prime Minister Ariel Sharon has been accused of undermining peace prospects after he ordered the speeding up of work to complete Israel's West Bank separation barrier.
Palestinian negotiator Saeb Erekat said Mr Sharon's order "undermines the efforts to revive the peace process.
"We urge the US and President Bush to exert maximum efforts in order to have Mr. Sharon comply with the cessation of violence and cessation of building the wall," Mr Erekat said.
Started over two years ago, the 425-mile barrier is still only about one-third completed. Israel claims it is necessary to stop Palestinian suicide bombers; Palestinians say the barrier is purely an attempt to annex even more Palestinian territory.
The most sensitive section is Jerusalem, where the route cuts the West Bank off from east Jerusalem, a traditionally Arab section that Palestinians claim as the capital of the state they want to create.
A source said Mr Sharon's order applies to the section surrounding Jerusalem - a sensitive part of the barrier that Palestinians contend is an attempt to take over part of the disputed city.
In appeals to Israel's Supreme Court, Palestinians have successfully challenged the route of the barrier in several places where it cuts villages off from their farmland or creates other hardships.
Some cases are still pending, blocking construction along key points.