Israeli Prime Minister Benjamin Netanyahu on Sunday said he was "gravely concerned" that attempts by world powers to sign a deal with Iran to curb its nuclear programme will succeed. "I'm concerned, gravely concerned, that this deal will go through and in one stroke of the pen, it will reduce the sanctions on Iran -- sanctions that took years to put in place -- and in return for this, Iran gives practically nothing," he said at a joint news conference with French President Francois Hollande.