Weekend talks among Mideast foreign ministers in Washington, D.C. produced joint concessions in the stalled Israel-PLO peace talks, including a Palestinian pledge to root out terrorists in Gaza and Israeli promises to pull back its troops from the region and allow Palestinian elections. After the talks concluded on Sunday, U.S. Secretary of State Warren Christopher said the concessions "will contribute significantly" to a Thursday summit between Israeli Prime Minister Yitzhak Rabin and PLO Chairman Yasser Arafat. But despite a personal appeal from President Clinton, Israel refused to end at once a 23-day closure of the Gaza border that aims to contain terrorists. Hundreds of Palestinians marched through Gaza City today in protest, saying the travel ban has kept them from their jobs in Israel and has paralyzed the local economy. An angry Arafat canceled an appearance, though, after turnout fell short of expectations.