Palestinian President Mahmoud Abbas is to meet U.S. President Barack Obama next week, ahead of the opening of the U.N. General Assembly, Palestinian sources said on Tuesday.

At their September 23 meeting, the two men will discuss peace negotiations between the Palestinians and Israel, which resumed earlier this year after a three year hiatus, the sources said.

Israel is to allow limited quantities of building materials for use by the private sector into the blockaded Gaza Strip starting from Sunday, a Palestinian official said.

After "efforts exerted by the Palestinian Authority, Israel has agreed for the first time in six years for building materials such as cement, iron and gravel to be brought into Gaza from Sunday" through the Kerem Shalom goods crossing, Raed Fattouh, PA official in charge of Gaza supplies, told Agence France Presse Tuesday.

Negotiators were holding peace talks in Jerusalem on Monday, Palestinian officials told AFP, although Israeli sources refused to confirm the meetings.

Meetings between the two sides, launched in Jerusalem in August, have been mostly held in secret under a U.S.-requested media blackout, and the Palestinian sources declined to be identified.

U.S. Secretary of State John Kerry met Palestinian President Mahmud Abbas in London, having earlier insisted that Israelis and Palestinians were determined to pursue direct peace talks.

Kerry met Abbas at London's Ritz Carlton on Sunday evening, the pair smiling and joking before holding a three-hour private meeting, their first talks since direct negotiations between the Israelis and the Palestinians began last month.

U.S. Secretary of State John Kerry will meet Palestinian president Mahmoud Abbas in London on Monday to discuss the direct talks between Israel and the Palestinians, U.S. officials said Thursday.

Kerry, who has met with Abbas numerous times over the past five months, will next see him at the end of a September 6-9 trip that will also take him to Lithuania and France, State Department spokeswoman Jen Psaki said.

Jordan's King Abdullah II and Palestinian president Mahmoud Abbas called Wednesday for a "comprehensive" solution in Syria, as Washington and its allies considered military action against the kingdom's northern neighbor.

"The king and Abbas discussed the Syrian crisis and urged a comprehensive solution to the crisis that would end the suffering of the Syrian people," a palace statement said after the two leaders met in Amman.

Palestinian president Mahmoud Abbas said Thursday all key issues were discussed at a new round of peace talks with Israel, but he declined to elaborate because of an agreed news blackout.

"We can't speak now about what happened," he told a joint press conference with U.N. chief Ban Ki-moon at his headquarters in the West Bank city of Ramallah.

Israel freed 26 Palestinian prisoners on Wednesday, hours before the two sides were to hold new direct peace talks amid a growing row over settlements.

A group of 15 crossed into the Gaza Strip at about 1:40 am (22:40 GMT) and were mobbed by relatives as they got out of a bus next to the border.

Palestinian president Mahmoud Abbas is committed to pursuing peace talks with Israel despite the unresolved issue of Israeli settlement building, U.S. Secretary of State John Kerry said here Tuesday.

"I'll be talking to president Abbas today ... and he is committed to continuing to come to the negotiation because he believes that negotiation is what will resolve this issue," Kerry said in Brasilia.

Palestinian president Mahmoud Abbas has asked caretaker prime minister Rami Hamdallah to stay on, tasking him on Tuesday with forming a new government, a spokesman said.

"Abbas on Tuesday met head of the caretaker government Rami Hamdallah and tasked him again with forming a government," the Palestinians' Wafa news agency quoted Abbas spokesman Nabil Abu Rudeina as saying.