The National Football League is exploring options for its media properties including selling stakes to strategic partners, a move aimed at expanding the reach of its television networks and digital services, the league told team owners in a letter Wednesday.

The league said it has hired Goldman Sachs Group Inc. to explore potential partnerships for the properties, which include the NFL Network and RedZone pay-TV channels as well as NFL.com.

The decision to seek partners is motivated by the league’s belief that its TV and digital holdings will benefit from being aligned with bigger media and technology companies rather than remaining stand-alone operations, league and team officials said.

“As the whole world of communications and digital media changes, we want to find a partner who can further help us maximize the reach and potential the NFL assets represent,” said New England Patriots owner Robert Kraft in an interview. Mr. Kraft is chair of the league’s media committee.

League and team officials stressed that they aren’t looking to sell the networks, and said the NFL will maintain control of them.

“We are not selling. We are looking for investment partners,” said Dallas Cowboys owner Jerry Jones in an interview. Mr. Jones is a member of the league’s media committee and chairman of the owned and operated media committee, which includes the NFL Network and RedZone.

Jerry Jones, owner of the Dallas Cowboys, on the field in Frisco, Texas, last month.

Jerry Jones, owner of the Dallas Cowboys, on the field in Frisco, Texas, last month.

Photo: Lola Gomez/The Dallas Morning News/Associated Press

In its letter to team owners, the league said it is aiming to create “an even more dynamic media asset that extends reach and engagement and creates additional value for the clubs—including through direct-to-consumer opportunities, new and innovative content and formats, and international expansion.”

In a memo to staff, NFL Commissioner Roger Goodell said the league has “a number of rights and assets to support the future growth of our business” including live games, tentpole events such as the NFL draft and “a myriad of opportunities around legalized sports betting.”

While there is no firm timetable for the hunt for potential partners, the commissioner said the process would likely run into and potentially through the 2021 NFL season.

NFL Commissioner Roger Goodell in May.

NFL Commissioner Roger Goodell in May.

Photo: Tony Dejak/Associated Press

That decision comes just months after the league wrapped up lucrative new long-term TV and streaming-rights deals valued at more than $100 billion.  The league also secured a 10-year collective-bargaining agreement with its players in 2020.

Bringing in new media partners would enhance the NFL’s financial strength, Mr. Jones said, adding that it also presents a rare opportunity to have a stake in the league, which is usually limited to team owners.

The NFL Network and RedZone are the league’s biggest media assets. The former is a year-round news and entertainment platform dedicated to football and carries seven regular-season games. It is in 56 million homes, according to S&P Global Market Intelligence’s Kagan unit.

A stake in the league is usually limited to team owners.

A stake in the league is usually limited to team owners.

Photo: Peter Joneleit/Associated Press

RedZone is an in-season Sunday-only channel that provides both highlights and live action from all the afternoon games. The commercial-free channel is particularly popular among fantasy football players. It isn’t as widely distributed as the NFL Network.

Both networks are facing the same challenges with cord-cutting as other channels. Other media companies such as Walt Disney Co. and AT&T Inc.’s WarnerMedia are focusing on building up their direct-to-consumer relationships. The NFL wants to keep pace and find new ways to exploit its content. To achieve that, Mr. Kraft thinks the league needs an assist.

“I’m not sure we are the best at taking advantage of what we have in our system,” Mr. Kraft said, adding that whether the league partners with a traditional media company, tech firm or startup, “we would just want to be with someone who is hungry.”

The NFL’s other properties include NFL.com, its NFL app, production facilities and library. The league’s media operations, currently based in West Los Angeles, are moving to new offices adjacent to SoFi Stadium, home of the Rams and Chargers.

Mr. Kraft said the league isn’t under any pressure to get a deal done. “We’re only going to do it if it’s the right fit. It has to be clear that it’s someone who can manage our resources better than we can,” he said.

Write to Joe Flint at joe.flint@wsj.com