Israeli Prime Minister Benjamin Netanyahu says he is going to the United Nations to "tell the truth in the face of the sweet talk and the onslaught of smiles," a reference to Iran's diplomatic overtures to the West.
It is the Israeli government's first reaction to last week's telephone call between US President Barack Obama and Iranian President Hassan Rouhani, the first such phone call between US and Iranian presidents in three decades.
Mr Netanyahu is travelling to the US to meet with Mr Obama and to address the UN General Assembly.
The Israeli leader is sceptical about Mr Rouhani. Israel believes Iran is continuing to build nuclear weapons capability and that it threatens Israel.
The statement on Sunday carried remarks made by Mr Netanyahu as he boarded the plane to New York the night before.