Britain, France and Germany have launched action under the Iran nuclear agreement paving the way for possible sanctions in response to Tehran’s attempts to roll back parts of the deal, European Union foreign policy chief Josep Borrell said Tuesday. The three countries, which signed the international agreement in 2015 along with the United States, Russia and China, informed Borrell, who supervises the pact, in a letter that they are triggering its “dispute mechanism,” ratcheting up pressure on the Islamic Republic. The powers said they are referring “this matter to the Joint Commission under the Dispute Resolution Mechanism, as set out” in the nuclear deal.