Shell plans to acquire Tri Star Energy in a deal that would more than double its company-owned convenience store footprint in the U.S.

The British energy company, which already has a 33% stake in Tri Star, said Tuesday that Equilon Enterprises, doing business as Shell Oil Products US, agreed to acquire the remaining interest in the convenience store operator and fuel distributor from Parman Corp, Kimbro Oil and its subsidiaries.

Shell did not disclose the financial terms of the deal.

The acquisition would make Shell the owner of an additional 320 fuel and convenience retail sites in Tennessee and surrounding states, as well as supply agreements with 552 more dealer-owned locations, the company said.

Shell has a sweeping footprint of 12,000 branded gas stations and convenience stores across the U.S., but they are primarily wholesaler- and dealer-owned. The deal for Tri Star aims to strengthen Shell's company-owned footprint in the U.S., the company said.

Shell said the transaction is part of its strategy to shift capital toward areas where it has competitive advantages. The company has previously said it would focus spending in its mobility and convenience business on 10 key markets, including the U.S.

The deal is expected to close by year end, subject to regulatory clearance.