[12][14] He was appointed deputy foreign minister in 1930 replacing Abdullah Al Damluji in the post, an Iraqi adviser of King Abdulaziz.
[16] Following the establishment of the council of deputies in December 1931, Hamza was made one of its four members as the undersecretary of foreign affairs.
[18] As the undersecretary of foreign affairs Hamza signed an amity treaty on behalf of Saudi Arabia with Egypt in Cairo on 7 May 1936.
[19] Through the treaty, Egypt recognized Saudi Arabia as an independent and sovereign state, and diplomatic relations between the two countries began.
[20] However, Hamza met with David Ben-Gurion, chairman of the Zionist and Jewish Agency Executive, at his Beirut home on 13 April 1937.
[11] In this unofficial meeting Ben Gurion attempted to get information about King Abdulaziz's views on the formation of a Jewish state in the Middle East, and Hamza suggested him to meet with Ibn Saud as well as Crown Prince Saud and Yusuf Yasin during the latter's visit to London for the coronation of King George VI.
[11] Hamza visited Germany to negotiate arms sales and met with the Nazi officials in the period 23–27 August 1938.
[15] In November 1941 the King sent him a telegram stating that his attempts would be harmful for Saudi Arabia, and ordered him to terminate all his relations with Nazi officials.