The United Nations envoy to Syria is calling for a truce in the northern city of Aleppo as a building block to a wider resolution of the country's grinding civil war.

U.N. envoy Staffan de Mistura spoke at a news conference Tuesday in the capital, Damascus. His public call for a cease-fire came a day after Syrian President Bashar Assad said the suggestion was "worth studying."

Previously, pro-government Syrian media lashed out at de Mistura, accusing the international diplomat of overstepping his bounds for suggesting local truces throughout Syria.

Aleppo was Syria's former commercial hub and is now the last major city where rebels still hold large areas, although they are under increasing attack from advancing government forces.

De Mistura is on a three-day visit to Syria.