UN chief Ban Ki-moon called on Israelis and Palestinians on Friday to overcome "deep scepticism" that he said risked thwarting efforts to reach a peace agreement.
"We must overcome the deep skepticism that comes from 20 years of stalemate," Ban said at a meeting in Jerusalem with Israeli President Shimon Peres.
"I urge all parties to avoid actions that risk undermining the negotiations," a statement quoted him as saying.
"Both sides need to sustain an environment conducive for the peace process to move forward," he said speaking two days after peace talks resumed in Jerusalem.
Ban Ki-moon's comments come as a survey reveals that most Israelis are no longer willing to make concessions to the Palestinian Authority - the result of a widely-held belief that regardless of Israeli concessions the "core issues" of the conflict are insurmountable.
The most recent territorial concession - the expulsion of 9,000 Jews from Gaza and parts of northern Samaria (Shomron) in 2005 - was reciprocated by the firing of thousands of rockets onto Israeli civilians by Gaza-based terrorists. That has been widely seen as contributing to the hardening of Israeli attitudes against calls to make more "painful concessions" as urged by western leaders.
Wednesday's talks, the fruit of months of intensive US diplomatic efforts to bring the two sides back to the negotiating table after a nearly three-year break, were overshadowed by a row over Israeli construction plans in Judea and Samaria.
Ban criticized the Israeli plans at a meeting with Palestinian Authority Chairman Mahmoud Abbas on Thursday.
The UN chief told reporters he was "deeply troubled by Israel's continued settlement activity in the West Bank [Judea and Samaria], including east Jerusalem.
PA officials and their supporters have expressed anger at the plans, despite having been made aware of them prior to the start of talks, and despite the fact that the planned construction is to take place in areas which the PA has previously agreed would remain "part of Israel" in the "Two State Solution" they claim to support.
Later on Friday, Ban was to meet Israeli Prime Minister Benjamin Netanyahu, Justice Minister and chief negotiator Tzipi Livni, and Defence Minister Moshe Yaalon.