BEIJING, May 14 (Xinhua) -- China and Colombia should take the latter's formal accession to the Belt and Road Initiative as an opportunity to upgrade bilateral cooperation, Chinese President Xi Jinping said on Wednesday.Xi made the remarks when meeting with his Colombian counterpart Gustavo Petro, who is in Beijing for the fourth ministerial meeting of the China-CELAC (the Community of Latin American and Caribbean States) Forum.After their meeting, the two heads of state witnessed the signing of a cooperation plan between the two governments on jointly building the Silk Road Economic Belt and the 21st-Century Maritime Silk Road.