The US has stepped up the pressure on Syria, calling for a UN resolution to enforce sanctions by "all necessary means". <br /><br />Hillary Clinton refused to take military options off the table, in an effort to end a 13-month conflict, while UN Secretary General Ban Ki-moon wants to send more international observers to monitor the shaky ceasefire. <br /><br />Al Jazeera's Kristen Saloomey reports from the UN.
