WASHINGTON - US Secretary of State John Kerry on Wednesday acknowledged difficulty in promoting peace talks between the Israelis and the Palestinians despite his strenuous efforts for the past year.

The top American envoy pointed to the level of mistrust between the parties, which he called "as large as any level of mistrust I' ve ever seen."

Kerry leaves Middle East without achieving framework

"On both sides, neither believes the other is really serious," he told lawmakers at a House panel hearing on his agency's budget for fiscal year 2015. "Neither believes that the other is prepared to make some of the big choices that have to be made here."

"I still believe it's possible but difficult, and so we're gonna proceed as privately as we have," he added. "I do believe both parties are serious. Both parties want to find a way forward. "

Kerry had aimed for a deal on all the final-status issues -- security, border, the status of Jerusalem and refugees, within nine months when he brought back the Israelis and the Palestinians for fresh negotiations in late July last year after a hiatus of three years.

However, no visible progress has been made so far despite Kerry 's hard push in his ten visits to the region in the past year, as the parties have been wrangling over settlement building on the occupied land, security arrangements and other issues.

"I must say, most of the details are not out in the marketplace of conversation, but there've been enough public dramatic statements of one position or another that I think gets in the way of the negotiation," Kerry said.

The Obama administration is trying to sell off a framework plan to both sides that will guide negotiations by sketching the outlines of an accord, as Kerry said late last month that the ongoing talks would slip beyond the original deadline of April 29.