CAIRO – Egypt's opposition alliance urged supporters Wednesday to vote “No” in the referendum on a disputed constitution rather than boycotting, hours after the Islamist government forged ahead by starting overseas voting in diplomatic missions for expatriates. “We call on citizens to vote ‘no' in the referendum on the constitution,” Egypt's opposition National Salvation Front said in a statement read out by spokesman Khaled Dawud at a Cairo news conference. But it added that that position would change to a call for a boycott if four conditions were not met. They were that judges monitor every polling station; that security be ensured both inside and outside; that the vote be monitored by both Egyptian and international observers; and that the referendum take place on a single day - this coming Saturday - as had originally been planned. The start of overseas voting after weeks of mass opposition protests showed the determination of President Mohamed Morsi to go forward with the process despite a three-week political crisis. Meanwhile, efforts to resolve Egypt's rapidly worsening political crisis suffered a blow Wednesday when the army abruptly postponed “unity” talks that the opposition had minutes earlier said they would attend. – Agencies