(Reuters) - SoftBank Group Corp is exploring a sale of Brightstar Corp, a U.S. cellphone distributor that could be valued at more than $1 billion (714.08 million pounds), people familiar with the matter said, as the Japanese technology conglomerate seeks to shed lower growth assets.

SoftBank Chief Executive Masayoshi Son has been reviewing the company's portfolio to pay down debt, which reached 15.8 trillion yen ($147 billion) as of the end of December. SoftBank said earlier this year that it plans to take its Japanese mobile phone unit public, with proceeds used to strengthen its balance sheet and boost growth.

SoftBank has hired investment bank JPMorgan Chase & Co (>> JP Morgan Chase & Company) to help explore options for Brightstar, the sources said this week. These options including selling Brightstar outright, offloading a substantial stake, or divesting some of its units, one of the sources said.

Brightstar has more than $10 billion in annual revenue, but runs a costly, low-margin business, and is expected to generate just $150 million in earnings before interest, taxes, depreciation and amortization this year, another of the sources said.

Brightstar could appeal to private equity firms, technology distribution companies or supply chain logistics companies in the United States or Asia, that same source added.

The sources asked not to be identified because the matter is confidential. Brightstar did not respond to a request for comment. JPMorgan and SoftBank declined to comment.

Brightstar is the exclusive provider of handsets to certain SoftBank affiliates. It also has a phone trade-in and cellphone insurance business. It was founded by Marcelo Claure, the CEO of U.S. wireless carrier Sprint Corp, which is now majority-owned by SoftBank.

Claure launched Brightstar in 1997 in Miami as a small distributor of mobile devices that has now expanded to about 70 countries on six continents, according to its website.

SoftBank acquired 57 percent of Brightstar in 2013 in a deal that valued the company at $2.2 billion. It later acquired more of the company.

SoftBank has shifted its attention in the last 12 months to deploying some $93 billion it raised for its Vision Fund, the world's largest private equity fund. Its backers include Saudi Arabia's sovereign wealth fund, Apple Inc and Foxconn, formally known as Hon Hai Precision Industry.

(Reporting by Liana B. Baker and Greg Roumeliotis in New York; Editing by Tom Brown)

By Liana B. Baker and Greg Roumeliotis