DALLAS — Natural gas company Energy Transfer Partners is buying Sunoco in a deal valued at about $5.3 billion.

The acquisition would expand the footprint of the Dallas company in the Northeast, and also diversify its holdings in a shift toward more crude and other heavy hydrocarbons. Natural gas companies have been hammered by plunging prices, which have recently hit 10-year lows.

“This transaction, which will be immediately accretive, represents the next step in Energy Transfer Partners’ transformation into a more diversified enterprise with an integrated and expanded footprint,” said Chairman and CEO Kelcy Warren.

Energy Transfer Partners said the deal will bring its cash flow mix for its pipeline businesses to about 70 percent natural gas, and 30 percent heavier hydrocarbons.

The offer includes $25 in cash and a portion of an Energy Transfer Partners unit totaling $50.13 for each Sunoco share.