Jan 22 (Reuters) - Motor fuels distributor Sunoco said on Monday it would acquire oil and gas transportation service NuStar Energy in an all-stock deal valued at about $7.3 billion, including assumed debt.

NuStar's common shareholders will receive 0.400 Sunoco shares for each NuStar common unit, implying a 31.9% premium to last close.

The companies said the deal has been approved by both their boards and have flagged synergies of $150 million by the third year following closing of the deal, expected to close in the second quarter of 2024.

Shares of Sunoco were down 2.5% in premarket trading, while shares of NuStar were up 26%. (Reporting by Seher Dareen in Bengaluru; Editing by Shailesh Kuber)