DOW JONES NEWSWIRES Williams Partners LP's (WPZ) bigger offer of 10 million of its common units priced at a 3.1% discount to its Tuesday close. Williams Partners units recently were down 3.8% at $54.19 in recent premarket trading, below the offer price of $54.56. Through Tuesday's close, they are down 6.2% this year. The company on Tuesday had unveiled plans to offer 9 million of its units to help fund its $2.5 billion acquisition of Caiman Eastern Midstream LLC. Williams Partners had about $305 million in common units outstanding as of Feb. 23. The offering comes a few days after Williams Cos. (WMB) raised $795 million in a public offering of 26 million shares to raise funds for the purchase. Williams Partners is the midstream and interstate gas pipeline asset-holder of Williams Cos., an energy company. Last month, Williams Partners unveiled its plans to buy Caiman, which has midstream facilities in the Marcellus Shale, a major unconventional shale-energy field that underlies several U.S. states. Pipeline companies in the U.S. are undergoing a wave of acquisitions and expansion as they seek to adapt to the new geography of energy production brought about by shale production. -By Tess Stynes, Dow Jones Newswires; 212-416-2481; Tess.Stynes@dowjones.com