Palestinian Authority (PA) Chairman Mahmoud Abbas met on Tuesday with Washington's Middle East envoy, hoping to secure a series of US guarantees before resuming peace talks with Israel.

George Mitchell returned to the region on Monday for the first time in months on a mission to salvage peace talks between Israel and the Palestinians a week after Washington admitted that direct negotiations were off the menu.

Mitchell is trying to secure Palestinian agreement to discuss the key issues of the conflict through indirect negotiations with the Israelis.

Central to the meeting was the US response to a list of Palestinian demands laid out in a letter handed to US Secretary of State Hillary Clinton last week by chief negotiator Saeb Erekat.

"Last week, Erekat delivered a letter to Clinton saying that they want US guarantees and answers before returning to any negotiations, direct or indirect," a senior Palestinian official speaking before the meeting told AFP. "We are now awaiting the answer to that letter."

But in a press conference following the meeting, Mitchell made no mention of the letter or any of its demands, saying only that Washington was determined to pursue its efforts to secure a peace deal.

"As we expected, there have been very many difficulties, obstacles and setbacks along the way," he said after several hours of talks with Abbas.

"We accepted it but we are determined to persevere in our efforts until we reach the conclusion that all want: an independent, viable state of Palestine ... living side by side in peace with Israel."

The letter had laid out two key requests on which the Palestinians are conditioning their return to any peace talks with Israel.

Firstly, it seeks US guarantees that there would be "a complete halt to settlement in the West Bank and East Jerusalem."

It also calls on the United States to recognise a Palestinian state based on 1967 borders.

If Washington refuses, the letter asks that it not take steps to prevent the Palestinians from seeking such recognition from the UN Security Council.