JERUSALEM — The Palestinian leadership on Thursday cautiously welcomed a proposal by international mediators to resume peace negotiations but said Israel had to first halt settlement building on occupied land, a demand rejected by Israeli Prime Minister Benjamin Netanyahu. The Palestinian position, issued after a meeting in Ramallah chaired by Palestinian Authority President Mahmoud Abbas, underlined the continuing impasse that has prevented a resumption of talks, even as the United Nations Security Council considers a Palestinian application for U.N.