NEW : more than 3,500 people have died in violence Sunday , an activist group says . The United Nations could impose economic sanctions Thursday if Syria ignores deadline . Syria is under international pressure to halt its crackdown on pro-democracy protesters . `` If they do not comply , then the league 's economic body will file a report to the foreign ministers of the league who will meet on Sunday to vote on the economic sanctions to be implemented , '' said the diplomat , who asked not to be named due to the sensitivity of the negotiations with Syria . The United Nations says At least 35 have died since the protests began in March .
NEW : more than 3,500 people have died in violence Sunday , an activist group says . The United Nations could impose economic sanctions Thursday if Syria ignores deadline . Syria is under international pressure to halt its crackdown on pro-democracy protesters . The United Nations says At least 35 have died since the protests began in March .