"On behalf of the Angolan executive and on my own, I congratulate you on your election to the position of director-general of the World Trade Organization, which took place on the 15th of the current month, in Geneva", said a note signed by João Lourenço.
In the note, the head of state said he was convinced that the appointment of the Nigerian woman, the first woman and the first African woman to lead the WTO, was "the clear recognition of her unequivocal competence, demonstrated convincingly in her previous duties".
"I wish you many successes in the performance of your new duties, on this great stage of international diplomacy", added João Lourenço.
Ngozi Okonjo-Iweala, 66, was appointed on Monday to head the WTO, becoming the first woman and the first African to lead the Geneva-based organization.
Ngozi Okonjo-Iweala was Nigeria's finance minister twice and headed the country's diplomacy for two months. She began her career in 1982 at the World Bank, where she worked for 25 years. In 2012, she failed to become president of the financial institution, which chose South Korean-born Jim Yong Kim for the job.
The new WTO leader was born in 1954 in Nigeria, but spent much of her life in the United States of America, where she studied at two prestigious universities, the Massachusetts Institute of Technology (MIT) and Harvard.
The WTO statutes have not provided for any geographic rotation for the Director-General, but several voices have argued that it is the turn of an African or an African to take office. Since its creation in 1995, the WTO has been led by six men: three Europeans, one New Zealander, one Thai and one Brazilian.
The Nigerian will take over the WTO from 1 March.