TEL AVIV (AFP) - US-led efforts to broker a resumption of peace talks ended on Sunday without a breakthrough, a top Palestinian official said, although Washington's top diplomat hailed "real progress".

US Secretary of State John Kerry has spent the past four days locked in intensive shuttle diplomacy between the Israeli and Palestinian leadership in a high-profile bid to draw the two sides back into direct negotiations after a gap of nearly three years. But after 13 hours of talks with Israeli Prime Minister Benjamin Netanyahu, and around six hours with Palestinian President Mahmud Abbas, Mr Kerry's marathon efforts ended on Sunday with little sign of progress.

Speaking in Ramallah after Mr Kerry held his third and final meeting with Mr Abbas, chief negotiator Saeb Erakat said there had been "no breakthrough".

"It was a positive and profound meeting with President Abbas, but there has been no breakthrough so far and there is still a gap between the Palestinian and Israeli positions," he told a news conference.

But Mr Kerry himself insisted he had had "very positive" discussions with both sides since beginning his shuttle diplomacy in Jerusalem on Thursday evening.

"We agreed we have made real progress, but we have a few things we need to work on," he said after a final meeting with Mr Abbas before heading off to Asia.

"We both feel good about the direction," he said.

Speaking at the start of the weekly Cabinet meeting, Mr Netanyahu insisted that Israel was not blocking a return to negotiations.

"We are not putting up any impediments on the resumption of the permanent talks for a peace agreement between us and the Palestinians," he said in remarks communicated by his office.

"There are things that we will strongly insist on in the talks themselves, especially security... There will be no agreement that will endanger Israelis' security."

He also pledged to put any agreement to a referendum, saying it will be "submitted to the people for a decision". But Israel's army radio Mr said Kerry's marathon efforts had so far failed to coax the sides back into direct negotiations after a gap of nearly three years.

Mr Abbas is pushing Israel to free the longest-serving Palestinian prisoners, to remove roadblocks in the West Bank and to publicly agree to make the lines that existed before the 1967 Middle East war the baseline for negotiations.

Army radio said that Mr Netanyahu was willing to consider just the first two conditions - but only after talks were under way.

So far, Israel has flatly refused to countenance any return to the 1967 lines.

Palestinian officials appeared pessimistic about Mr Kerry's chances of achieving a breakthrough.

"Netanyahu and his government are not serious about establishing a Palestinian state in the 1967 borders. They speak of a state without clear borders, and we need clarity according to international resolutions," said Mr Azzam al-Ahmed, a senior official of Abbas' ruling Fatah party.

"We are ready to resume negotiations according to our clear guidelines," he told Voice of Palestine.

In another move likely to spark tension, army radio said an Israeli committee was poised to push through a big discount for buyers of nearly 1,000 new homes which are due to be built in annexed east Jerusalem.

Last week, on the eve of Mr Kerry's arrival, another local committee gave final approval to build some 70 homes in the same area.

Palestinian chief negotiator Saeb Erakat said it showed which side was blocking a return to the negotiating table.

"This is Netanyahu's response to everything Kerry said, to his ideas and to all his efforts," Mr Erakat told AFP.

"We on the Palestinian side tried every possible effort to help Kerry succeed but it is obvious today... that Netanyahu is putting an obstacle in front of Secretary Kerry's efforts."

Mr Kerry, who has made the elusive goal of Middle East peace a top priority, was on his fifth visit to the region since taking over the State Department in February.