Israel does sincerely negotiate. The Palestinians do not because in the end they refuse to agree to any deal that does not involve Palestinians returning to Israel-proper within the 1948 boundaries, which would destroy Israel as a Jewish state. On the other hand, Israel is sincere. "In every round of talks with the Palestinians, Israel has acknowledged that many settlements will be dismantled under a future agreement." http://www.molad.org/images/upload/files/settleeng.pdf