The State Department was unable to say on Wednesday whether Secretary of State John Kerry will attend a planned May 30 meeting in Paris.
And outside experts say Washington is unlikely to want to allow France to take the lead on an issue that it traditionally sees as its own.
"We remain concerned about the continued violence on the ground and we welcome all ideas on moving this forward," US spokeswoman Elizabeth Trudeau said.
"On this specific conference, on the May 30 event, no decision's been made on participation."
"We still remain in consultation with the French and other international partners on it," she said.
Kerry was in Paris on Monday to see his counterpart Foreign Minister Jean-Marc Ayrault, and his deputy Antony Blinken was there again on Wednesday.
France's prime minister, Manuel Valls, will visit Israel and the Palestinian territories this month to try to drum up interest in the French initiative.
But Israel opposes the plan to bring ministers from 20 countries to Paris, insisting peace will come only through direct talks with the Palestinians.
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And there is clearly little enthusiasm in Washington.
"They're reluctant on at least two fronts," said Ghaith al-Omari, a fellow of the Washington Institute of Near East Policy and a former adviser to Palestinian peace negotiators.
"One front is that there's always been American reluctance to engage in anything about the peace process that is not American led," he told AFP.
"The other component is that the administration has not decided yet whether or not they will be doing something American in the next few months."
Reports in Washington have suggested that President Barack Obama, due to leave office in January, may be planning a major speech to outline terms for peace.
And Washington may decide to take a blueprint for the "two-state solution" to the conflict to the UN Security Council to be enshrined in international law.
But Obama has yet to decide whether to insert himself into an issue that has frustrated so many of his predecessors -- or whether to let the French try.
"Until there's a decision it's unlikely that the US will engage in any external initiatives," Omari said.
"If the president is going to give a speech I can't see Kerry going to the French initiative. If not then there might be more space for American engagement."