Muallem was a member of the Syrian Regional Branch of the Arab Socialist Ba'ath Party. Muallem began his career at foreign ministry in 1964 and served in Syrian missions to Tanzania, Saudi Arabia, Spain and the United Kingdom. During his tenure in Saudi Arabia Muallem was a political attache. In May 1967 he and another Syrian political attache in Saudi Arabia, Jaber Bajbuj, were declared persona non grata by the Saudi authorities due to their alleged contacts with Ba'ath agents in Saudi Arabia, and both were ordered to leave the country within 24 hours.