The United States has warned that the Palestinian bid for UN membership could \"derail\" Middle East peace efforts, ahead of a new international attempt to bring Israelis and Palestinians back to negotiations. The two sides, who will meet international mediators in Jerusalem on Wednesday, remained at loggerheads over the deadlocked peace process as UN Security Council powers made new appeals for full negotiations, which if they fail could risk new violence. Mediators from the diplomatic Quartet - the European Union, Russia, United Nations and United States - are to meet separately in Jerusalem with Israeli and Palestinian representatives to try to break the impasse. The new Quartet initiative was launched the day that Palestinian President Mahmoud Abbas made his September 23 bid for Palestinian membership of the UN, which the United States has vowed to veto. The Palestinian membership campaign \"will not advance the peace process, but rather will complicate, delay and perhaps derail prospects for a negotiated settlement\", US ambassador Susan Rice told the Security Council meeting. The US and Israeli governments say that only new direct talks can reach the accord needed to set up a Palestinian state. Rice said the US administration was working \"vigorously\" with all sides to resume talks frozen since September last year.