JERUSALEM (AFP) - US Secretary of State John Kerry said on Sunday that any Middle East peace plan would be "fair and balanced," as he held a fourth day of talks with Israeli and Palestinian leaders.

"I can guarantee all parties that President (Barack) Obama and I are committed to putting forward ideas that are fair and balanced, and to improving the security of all peoples," Kerry told reporters in Jerusalem.

Kerry insisted on Saturday that there had been "progress" in the talks that he kick-started in July, despite bitter recriminations by both sides and mostly irreconcilable demands for any future peace deal.

"We're not there yet, but we are making progress," Kerry said Saturday, adding everyone was "working with great intensity" to try to reach a deal.

"I'm confident that the talks we've had in the past two days have already fleshed out and even resolved certain kinds of issues and presented new opportunities for others," he said.

"We are beginning to flesh out the toughest hurdles yet to be overcome." The US top diplomat was to set off early on Sunday for Jordan and then Saudi Arabia, after three days of intense shuttle diplomacy between Israeli Prime Minister Benjamin Netanyahu and Palestinian president Mahmud Abbas.

Jordan is one of only two Arab countries with Egypt to have signed a peace treaty with Israel, and King Abdullah II holds a special position because the treaty recognises his country's "historic" role in caring for Muslim holy sites in Israeli-annexed Arab east Jerusalem.

Saudi King Abdullah also plays a key role, as the kingdom was the author of a 2002 Arab League peace initiative.