On 4 July 1990, Cyprus formally applied to join the EC. The Turkish Cypriots and Turkey, which had applied for membership in 1987, were outraged. Denktaş claimed that Cyprus could only join the Community at the same time as Turkey and called off all talks with UN officials. Nevertheless, in September 1990, the EC member states unanimously agreed to refer the Cypriot application to the Commission for formal consideration. In retaliation, Turkey and the TRNC signed a joint declaration abolishing passport controls and introducing a customs union just weeks later. Undeterred, Javier Pérez de Cuéllar continued his search for a solution throughout 1991. He made no progress. In his last report to the Security Council, presented in October 1991 under United Nations Security Council Resolution 716, he blamed the failure of the talks on Denktaş, noting the Turkish Cypriot leader's demand that the two communities should have equal sovereignty and a right to secession.