In July 1976, following the establishment of the Socialist Republic of Vietnam as a reunified country, Phnom Penh Radio broadcast a commentary which proclaimed the "militant solidarity and friendship between peoples of Democratic Kampuchea and the Socialist Republic of Vietnam grow constantly greener and sturdier". However, during that same month, Pol Pot publicly hinted at tensions between Vietnam and Kampuchea when he told a visiting Vietnamese media delegation that there were "obstacles and difficulties" in the relationship between the two countries. Nonetheless, on 21 September 1976, the first air service connecting Hanoi and Ho Chi Minh City with Phnom Penh was established. Then in December 1976, the Kampuchean Revolutionary Organisation sent greetings to the Vietnamese Communist Party during their Fourth Congress.