Israel has introduced what it said was a new U.S. ceasefire plan and is trying to force Hamas to accept it by imposing a siege on the Gaza Strip.

Hamas will not agree to extend the first phase of the Gaza ceasefire deal as requested by Israel, a senior Hamas official said Sunday. Speaking to Al Jazeera, Mahmoud Mardawi said Hamas would only release the remaining Israeli hostages under the terms of the already agreed-upon phased deal.

Hamas accused Israel of trying to derail the ceasefire agreement hours after its first phase ended. It called the decision to cut off aid “cheap extortion, a war crime and a blatant attack” on the truce,