By Irene Klotz

CAPE CANAVERAL, Florida (Reuters) - Boeing Co plans to build space taxis at a mothballed space shuttle processing hangar at Kennedy Space Center in central Florida, according to company sources.

The company has reached agreement with Space Florida, a state-backed agency working to expand space-related businesses in Florida, to lease the Orbiter Processing Hangar Bay 3 at the center, Boeing spokeswoman Susan Wells said on Friday.

Wells said details of the lease agreement would be announced on Monday. Sources familiar with the plan said it would center on the space taxi manufacturing venture.

Kennedy Space Center is drafting a master plan for a revamped spaceport that, in addition to supporting future NASA spacecraft, will host commercial, military and international customers.

Boeing is one of four companies NASA is sponsoring to develop spaceships that can ferry astronauts to the International Space Station, a $100 billion project of 16 nations orbiting 240 miles above Earth.

With the retirement of NASA's space shuttles this summer, the United States is currently dependent on Russia to fly crews to the orbital outpost, at a cost of about $350 million per year.

NASA hopes to be able to buy rides from U.S. firms before the end of 2016.

Boeing's proposed space taxi is a seven-seat capsule called the CST-100, which would launch on an Atlas 5 rocket.

The company also has an agreement to provide rides for clients of Bigelow Aerospace, which is developing privately-owned inflatable space habitats for commercial and government lease.

NASA has spent $388 million to bolster the development of passenger spaceships. Boeing won $18 million in the program's first round of financing and $92.3 million in the second phase, which is currently under way.

The U.S. space agency this year added $20.6 million in options to Boeing's agreement if the company can complete additional milestones in the CST-100 development.

The Obama administration is requesting $850 million for the program for the fiscal year that began October 1. Bills pending in the U.S. House of Representatives and Senate would cut that to $312 million and $500 million, respectively.

(Editing by Tom Brown and Paul Simao)