Iran has released two US patrol boats and 10 crew members who were taken into custody on Tuesday after Tehran said they strayed into Iranian waters “unintentionally”. The swift resolution to the incident in the Gulf appeared to remove a potential flashpoint between the two countries just days before last year’s landmark nuclear deal is supposed to be implemented. Iranian and American officials said that the prompt release of the sailors was the result of the strong working relationship built up during the nuclear talks between John Kerry, US secretary of state, and Mohammad Javad Zarif, the Iranian foreign minister. However, images broadcast in Iran of the US sailors being detained with their hands behind their backs and on their knees could spark a backlash in the US Congress. The two governments also appeared to disagree over whether an apology had been issued. According to US officials, the incident happened near Farsi Island in the middle of the Gulf when a mechanical failure on one of the boats caused them to drift into Iranian territorial waters.