Work to re-purpose a launch complex at Florida's Cape Canaveral to support human space flights could create 250 to 300 new jobs, officials say.

United Launch Alliance, the company that provides launch services for NASA, said it has selected Hensel Phelps Construction Co. of Orlando to help plan modifications to Space Launch Complex 41 to prepare it for commercial crew missions using Atlas V launch rockets, Florida Today reported Thursday.

In work expected to take 21 months, Hensel Philips will work with ULA in the design and development of an access tower that would allow astronauts to enter a spacecraft sitting atop Atlas rockets, along with other modification to the complex.

"We look forward to working with Hensel Phelps to take the next steps in launching crew from SLC-41 and providing safe and reliable crew launch services as early as 2015," George Sowers, ULA vice president of Human Launch Services, said in a statement.

Three private companies -- Boeing, SpaceX and Sierra Nevada Corp. -- are developing space capsules for NASA's Commercial Crew Program.