Feb. 25 (UPI) -- Colombian President Gustavo Petro signed a formal request to begin convening a National Constituent Assembly, joining members of his Cabinet at a ceremony in Cartagena. The initiative , the government said, responds to what it describes as an "institutional blockade" that has hindered approval of several social and economic reforms promoted by the executive branch. The call for a constituent assembly, already authorized by the relevant electoral authority, requires support from