Mero became a member of the Ba'ath Party in 1966. He joined the Arab Teachers' Union becoming its secretary general for cultural affairs and publications. He served as governor of the Daraa province from 1980 to 1986. He was appointed governor of the Al Hasakah province in 1986 and served in the post until 1993. In 1993, he became governor of the Aleppo province and was in office until 2000. Despite regional tensions between Syria and Turkey at the time, he was said to have enjoyed good relations with the Turkish government and was integral in dealings between the two governments. In June 2000, he became a leading figure in the Baath party. On 7 March 2000, shortly before the death of President Hafez al-Assad, Mero was appointed as prime minister. Mero replaced Mahmoud Zuabi, who had been in office since 1987, as prime minister. Mero's cabinet was announced on 13 March 2000, and was tasked with tackling economic reforms and combatting corruption. After the death of Assad in 2000, a 9-member committee was formed to oversee the transition period, and Mero was among its members. He was retained by the new president, Bashar Assad, and was promoted within the ranks of the ruling Baath Party. Mero headed a ministerial and commercial delegation to neighboring Iraq in August 2001, becoming the first Syrian prime minister to visit the country since the Gulf War. In December 2001, in an effort to stimulate economic reform, Mero was charged with forming a new cabinet, which saw extensive reorganization with several "pro-reform" ministers appointed to strategic portfolios related to the economy. His premiership also oversaw improving ties with Turkey. In July 2003, Mero became the first Syrian prime minister to visit Turkey in 17 years, where he signed three agreements on health, oil and natural gas, and customs matters. Mero resigned form office in early September 2003, reportedly due to the stagnation of the process of economic reform. Then Parliament speaker Mohammed Naji Al Otari replaced him as prime minister. Mero continued his political career as a member of the central committee of the Ba'ath Party. His term ended in June 2005, and he retired from politics.
