Question: The diplomatic agreement between South Africa, Angola, and Cuba was observed by the USSR and what other country?
Sentence: Attempts to persuade South Africa to agree to the plan's implementation were not successful until 1988 when the transition to independence finally started under a diplomatic agreement between South Africa, Angola and Cuba, with the USSR and the USA as observers, under which South Africa agreed to withdraw and demobilise its forces in Namibia.
Answer in sentence: yes