Price estimated at up to $635 million

While several details still need to be fine-tuned, two prominent league sources told ESPN.com late Sunday night that Arizona businessman Reggie Fowler has reached an agreement in principle to purchase the Minnesota Vikings.

The Vikings scheduled a news conference for 3:30 p.m. ET, but did not confirm the subject or the guests.

If Fowler is successful in finalizing the deal with current Vikings owner Red McCombs, he would become the first black owner in modern NFL history.

"In terms of the dollars, the financing, payment schedules and such, everything seems to be pretty well set," one source said. "I think they'll be prepared to present the pertinent information (to the league) in relatively short order."

The purchase price for a team McCombs bought in 1998 for $246 million will be between $625 million to $635 million. Minnesota would become, if the sale to Fowler and his partners is consummated, the first NFL franchise to change ownership since Arthur Blank purchased the Atlanta Falcons in 2002 for $545 million.

McCombs has been attempting to sell the team for two seasons and, while he has had some suitors in the past, he has steadfastly held out for a price of at least $600 million. One of those past suitors, Glen Taylor, owner of the NBA's Minnesota Timberwolves, acknowledged this week that he recently forwarded McCombs a formal offer in which the purchase price would have escalated if the Vikings succeeded in landing a new stadium.

Over the past several years, McCombs has attempted unsuccessfully to convince the state legislature to approve a new stadium for his franchise.

Fowler has been working on the acquisition of the Vikings for several months and his pursuit of the franchise accelerated in recent weeks, as he and McCombs entered into an exclusive negotiating period.

Fowler, 46, who played linebacker at the University of Wyoming and had a brief stint as a pro, is the founder of Spiral Inc., a Chandler, Ariz.-based company with diversified holdings that include paper products and cleaning supplies, an aviation firm, a foam-manufacturing plant and a cattle ranch. The group Fowler has assembled to buy the Vikings includes some prominent New York-New Jersey real estate magnates.

It is expected Fowler would be the managing partner and according to the NFL ownership rules, he would be required to have at least a 30 percent interest in the club. On Feb. 4, the group Minnesota Vikings Football LLC was incorporated in Delaware and, while records do not reveal the shareholders, it is believed to be the Fowler group.

Any franchise purchase must be approved by the league finance committee and then by a three-quarters vote of the 32 owners. That process could take months to complete. The next scheduled owners meeting is the annual league session March 20-23 in Maui, Hawaii.

Taylor has broadly suggested in recent days that Fowler and his partners might have a difficult time garnering league approval of the sale. Taylor has said he is prepared to pursue the team if the Fowler deal falls through.

Len Pasquarelli is a senior NFL writer for ESPN.com. To check out Len's chat archive, click hereInsider.