(Reuters) -BP said on Monday it would sell stakes in the Permian and Eagle Ford midstream assets of its U.S. onshore oil and gas business for $1.5 billion to funds managed by investment firm Sixth Street.

The sale comes as BP reviews how to develop its oil and gas production assets and cut costs as part of a $20 billion divestment programme by end-2027.

It has been under pressure from investors after years of underperforming rivals and also the target of activist investor Elliott.

BP's U.S. onshore oil and gas business, bpx energy, will hold a 51% stake in the Permian assets and 25% in the Eagle Ford assets after the deal, the oil major said.

(Reporting by Shashwat Awasthi in Bengaluru; Editing by Subhranshu Sahu)