A top Hamas official says the Palestinian group is losing faith in the United States’ ability to mediate a cease-fire in Gaza.

The Associated Press says the comment from Osama Hamdan came ahead of a new round of talks scheduled for this week.

He says Hamas will only participate if the talks focus on implementing a proposal detailed by U.S. President Joe Biden in May and endorsed internationally.

AP says the U.S. referred to it as an Israeli proposal and Hamas agreed to it in principle.

Both sides later proposed changes, leading each to accuse the other of obstructing a deal.

Hamas is especially resistant to Israel’s demand that it maintain a lasting military presence in two strategic areas of Gaza after any cease-fire, conditions that were only made public in recent weeks.