BAGHDAD, Iraq - As Marines step up preparations for military offensives on two major Iraqi cities, a number of Sunni Muslim leaders are forwarding a plan to establish the rule of law in those areas through peaceful means, with the promise of reducing the insurgency across a large swath of the country. The bid is led by groups that have encouraged violent resistance in central, western and northern Iraq since the U.S.-led invasion 18 months ago. The groups say they'll withdraw their support for violence if Iraq's interim government can reassure Sunni leaders wary of national elections, which are scheduled...