"All parties to the conflict, other than groups designated as terrorist organisations by the United Nations Security Council, must now ensure its effective implementation in order to restore the cessation of hostilities, enable the lifting of all sieges and allow sustained, countrywide humanitarian access to those in need as well as progress on the issue of detainees and missing persons," she said in an official statement.
On Friday, Russian Foreign Minister Sergei Lavrov and US Secretary of State John Kerry announced a new plan aimed at reducing violence in Syria, which includes a new ceasefire that will come into force on September 12.
Syria has been mired in civil war since 2011, with government forces loyal to President Bashar Assad fighting a number of opposition factions and extremist groups.
