ISTANBUL (AFP) - Top diplomats piled pressure on Turkey and Israel to make up Saturday after Ankara's decision to expel the Jewish state's ambassador in retaliation for last year's deadly Gaza flotilla raid. UN chief Ban Ki-moon, senior European foreign ministers and officials in Washington all urged the one-time allies to end their increasingly poisonous dispute that they worried could impact on the wider Middle East. But there seemed little prospect of an immediate end to their dispute as Turkey's foreign minister indicated that a legal challenge to Israel's naval blockade of the Gaza Strip would be launched in a matter of days. "I sincerely hope that Israel and Turkey will improve their relationship," Ban told reporters in the Australian capital Canberra. "Both countries are very important countries in the region and their improving relationship, normal relationship, will be very important in addressing all the situations in the Middle East, including the Middle East peace process." The UN leader said he had been trying to help the countries improve their relationship since May 31, 2010 when Israeli troops boarded a Gaza aid flotilla, leading to the deaths of nine people including eight Turks. Turkey pulled its ambassador out of Tel Aviv in the immediate aftermath of the raid but on Friday Foreign Minister Ahmet Davutoglu said ties would be further downgraded after a UN probe slammed the "excessive" force used in the raid, for which Israel has failed to apologise. Meanwhile, the Palestinian Authority on Saturday condemned a UN report into a deadly Israeli raid on a Turkish-led aid flotilla as a political document not based on international law. "This report is terrible and negative. It's a purely political report, it's not legal," Palestinian negotiator Saeb Erakat said of the report on the May 2010 raid which killed nine Turkish activists.