Jerusalem ? A top Mideast envoy criticized Israel in especially tough language for moving too slowly on negotiations to open Gaza’s borders, saying the country is behaving almost as if the withdrawal from the Gaza Strip never happened.

Without dramatic progress soon, a rare chance to revive Gaza’s shattered economy – and the peace process – will be lost, James Wolfensohn said in a letter to the U.N. secretary general and other international mediators obtained Monday by The Associated Press.

Violence, meanwhile, quickly escalated between Israel and the Palestinians after Israeli troops killed Luay Saadi, a top Palestinian fugitive, and a close accomplice in a pre-dawn shootout in the Tulkarem refugee camp in the West Bank. Saadi, the leader of Islamic Jihad’s military wing in the West Bank, was blamed for the deaths of 12 Israelis in attacks in recent months.

Islamic Jihad threatened revenge and launched at least two homemade rockets from Gaza into Israel, causing no injuries. Israel, which said it would not tolerate any attacks from Gaza since it pulled out of the territory last month, responded with an artillery assault on open fields in northern Gaza, the army said. There were no reports of injuries from the artillery.

Israel closed the Rafah crossing into Egypt, Gaza’s main link to the outside world, shortly before it withdrew from Gaza. It also has severely restricted the passage of Palestinian laborers and goods in and out of Israel, the main Palestinian export market, since an earlier wave of rocket attacks right after the pullout.

Israeli officials say the measures are solely because of security considerations.

In his letter, Wolfensohn, a special envoy working on behalf of the United States and other foreign mediators, acknowledged such concerns but accused Israel of unnecessary delays in restoring movement across the borders. He said the stalling is preventing him from moving on to larger reconstruction efforts.

“The government of Israel, with its important security concerns, is loath to relinquish control, almost acting as though there has been no withdrawal, delaying making difficult decisions and preferring to take difficult matters back into slow-moving subcommittees,” Wolfensohn wrote in the Oct. 17 letter to U.N. Secretary-General Kofi Annan.

He said the differences could be quickly resolved, and expressed disappointment he failed to reach a solution during a trip to the region earlier this month.