(Bloomberg News) Boston Properties Inc. and Hines formed a joint venture to develop San Francisco's tallest office building, a 61-story tower to be built adjacent to a new transit center in the South of Market area.

The companies will each have a 50 percent interest and agreed to acquire the project land for about $190 million from the Transbay Joint Powers Authority, the agency overseeing the transit center, Hines and Boston Properties said today in a statement. The transaction is expected to be completed in the first quarter of 2013.

"We are very gratified to have both a stellar partner and the city's nod of approval," Gerald D. Hines, chairman of Houston-based Hines, said in the statement. "We think the tower will be a beautiful addition to San Francisco's beloved skyline as well as an extremely desirable and sustainable workplace next to one of the state's busiest transit hubs."

Final approval for the 1.4 million-square-foot (130,000- square-meter) tower, designed by Pelli Clarke Pelli Architects, was granted by the San Francisco Planning Commission on Oct. 18. The 1,070-foot (326-meter) high-rise will be located next to the transit center at First and Mission streets. A 5.4-acre (2- hectare) rooftop park is planned for the center, which will connect 11 transit systems, according to the statement.

"The combination of our two organizations will provide superior management at all levels of this extraordinary project, which we are committed to make a landmark for generations to come," said Mortimer Zuckerman, chairman and chief executive officer of Boston Properties, based in Boston.