Hamas will not agree to extend the first phase of the Gaza ceasefire deal as requested by Israel, a senior Hamas official said Sunday.

"The extension of the first phase as proposed by the occupation is unacceptable to us, and the mediators and guarantor countries are required to oblige the occupation to abide by the agreement in its various stages," Hamas spokesman Hazem Qassem said in a statement.

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.