Citing "reliable sources," Der Spiegel reported that Israeli intelligence intercepted calls Kerry made on normal, non-encrypted phones while he attempted to broker a peace deal between Israel, Palestinians and Arab states. At least one other intelligence agency, which Der Speigel did not identify, also allegedly listened in on Kerry's calls.
The Israeli government then used information gleaned from Kerry's conversations in the failed peace negotiations, according to Der Speigel.
Both the U.S. State Department and Israeli authorities declined to give comment to the German weekly.
The report comes after the U.S. government had allegedly been fuming over Israeli criticism of Kerry over his attempt to broker a cease-fire between Israel and Hamas militants in Gaza. On Friday, President Barack Obama took a moment to give credit to Kerry for his fruitless efforts and defended him from "unfair criticism" over the doomed cease-fire negotiations.