"The American side has not participated in any meetings until now between Israel (and the Palestinians)," Palestine Liberation Organisation secretary general Yasser Abed Rabbo told Voice of Palestine radio.
"Washington said it would be a direct partner in talks but so far this hasn't happened because of Israel's insistence on keeping the US away from meetings," he said.
"If the US can't impose its presence, then it will not have any direct influence on achieving progress in negotiations," Abed Rabbo added.
The talks, which resumed last month after a three-year hiatus, have been overshadowed by Israeli plans to build more than 2,000 new homes for Jewish settlers on occupied Palestinian territory.
Abed Rabbo slammed the settlement expansion plans, saying they threatened the renewed peace efforts.
"Israel's continued and unrestricted settlement building is a danger to resumed talks, which could end in disaster," he said.