DOW JONES NEWSWIRES Williams Partners LP (WPZ) unveiled plans Tuesday to offer 6.5 million common units as the company looks to raise money to fund capital expenditures and for other general partnership purposes. Units slipped 3.4% to $62.65 after hours. The stock has climbed 38% in the past 12 months. Williams Partners, the midstream asset-holder of Williams Cos. (WMB), said some of the offering's proceeds likely will be used to help fund its planned acquisition of Laser Northeast Gathering System. Williams said it will make a cash contribution to Williams Partners to maintain its 2% general-partner interest in the partnership. As a result of the offering, Williams' limited-partner interest in Williams Partners will be reduced to approximately 72% from its current level of approximately 73%. Williams Partners had 290.5 million common units outstanding as of Nov. 1. In November, Williams Partners reported an increase in its bottom line for the third quarter on wider margins and higher pipeline fees. Last month, the company said it agreed to acquire Laser Northeast Gathering System and other assets in the Marcellus shale from Delphi Midstream Partners LLC in a deal valued at roughly $750 million. -By Nathalie Tadena, Dow Jones Newswires; 212-416-3287; nathalie.tadena@dowjones.com