IN the latest sign of ambitious growth plans, Google Inc has signed a 40-year lease to secure space for a huge office complex that will be built on a federal research center near the Internet search leader's Silicon Valley headquarters.

The 1.2-million-square-foot campus announced on Wednesday fulfills a vision that Google first laid out with the NASA Ames Research Center in 2005. The NASA center is within a 10-minute drive of Google's Mountain View base.

Google anticipates needing the additional space for the thousands of workers it expects to hire as it tries to mine more profits from the Internet's advertising market and expand into other areas of technology and media.

In the past four years, Google has added more than 17,000 employees to boost its payroll to 19,156 workers. The growth has prompted the company to lease or buy many of the smaller offices circling its headquarters, a 1-million-square-foot campus that Google purchased for US$319 million in 2006.

The NASA deal sets Google's initial rent for 42.2 acres of land at US$3.66 million per year. Google didn't estimate how much it would cost to build the new campus, which will begin construction in 2013 and will include some housing for employees. Google expects to start the final phase of the campus in 2022.

Google hopes the location of its new offices will make it easier to draw on the brain power of NASA's rocket scientists and give it another competitive advantage over its rivals.