Greece is geographically contiguous to Bulgaria, and relations between the two countries have been alternately hot and cold depending on the political climate of the times. In 1964 both countries signed an accord relative to war reparations, which opened up some channels of communication, cultural exchanges, and relaxed travel restrictions. The move toward better relations was interrupted by the 1967 coup d'etat in Greece, but improvement began again in the early 1970s when officials of the two governments exchanged visits. By 1972 a newly created Bulgarian-Greek economic cooperation commission had met in Sofia. Difficulties between Bulgaria and Turkey have deep roots in history and also involve the 750,000 ethnic Turks still residing in Bulgaria (see ch. 2; ch. 4). An atmosphere of cordiality, however, had been developing slowly as the officials of both countries cautiously negotiated to reduce tensions between the two countries. Exchanges of high-level visits and the signing of various economic agreements had stabilized Bulgarian-Turkish relations by the early 1970s. The hijacking of two Turkish planes to Sofia in 1972 disturbed the détente temporarily, but the Bulgarian foreign minister went quickly to Turkey to make amends. In 1973 the two countries again enjoyed improved relations. The United States The tensions that marked Bulgarian-United States foreign relations in the 1950s eased somewhat in the 1960s. The legations of both countries were raised to embassy status in November 1966. This action was believed to be an offshoot of United States efforts, particularly that of President Lyndon B. Johnson, to "build bridges" to Eastern Europe. This resumption of diplomatic goodwill was not pursued vigorously and, at the time, reception to the idea in Bulgaria was generally cool. A noted communist theoretician regarded the United States overtures as a divisive force in the fraternal world of the communist movement, designed ultimately to bring in a capitalist system inimical to the ideological interest of any socialist country. In 1973 the relations between the two countries were, however, cordial. Observers noted an increase in trade, although it was still quantitatively small and accounted for only between US$6 million and US$7 million annually. Bulgaria hoped to increase this volume to US$30 million, especially by exporting high-quality tobacco to the United States market.