SMU has agreed to pay $18.1 million to University Park to buy a park, streets and alleys needed to expand the campus, officials said Thursday.

The deal ends an impasse over the sale of Potomac Park, a three-quarter acre tract of undeveloped green space behind Park Cities Plaza on Mockingbird Lane.

University Park voters approved the park sale in 2007, but SMU balked at the price submitted by the city's appraiser.

The university and the city each got additional appraisals and both sides agreed to take the average of the two prices, which was about $2.2 million, or $62.63 per square foot.

The final deal, unveiled Thursday, includes the park and streets, alleys and rights of way in several locations around SMU.

"It's a win-win situation for both SMU and our city," University Park Mayor James H. "Blackie" Holmes.

University Park officials will vote on the sale next week.

SMU officials said they were happy to buy the streets and alleys because they have a master plan that calls for expansion in those areas.

SMU has long wanted more land, particularly now that plans are under way to build the George W. Bush Presidential Library along the eastern edge of campus at Central Expressway.

"It was a good time to be looking at any of the future requests we'd be making of the city," said Brad Cheves, SMU's vice president of development and external affairs.

Money for the $300 million Bush library is being raised by the George W. Bush Presidential Foundation, which will plan and build the structure. The land transaction will help that effort by giving SMU clear title to roads, alleys and easements on the future library site, Holmes said.

Meanwhile, SMU has its own capital campaign under way to upgrade and add academic buildings and student housing.

The Annette Caldwell Simmons Hall is in the construction planning phase in the northern part of the campus near University Boulevard. And new student housing is contemplated along the southern edge around the Park Cities Plaza and the former Mrs. Baird's Bread plant, which the university now owns.

City officials said money from the sale of Potomac Park will be used exclusively for park improvements. They have identified improvements at Coffee Park, the swimming pool at Curtis Park and a playground next to a new pump station at Germany Park.

The $15.9 million from the sale of streets, alleys, and utility easements will be held in a special reserve fund in the city's general fund while officials develop guidelines for its use.