Four months after lawmakers in Oregon approved legislation that tax rules would not change for companies making new investments in the state, sportswear giant Nike is to expand its headquarters in Washington County.

Nike said it intends to build two new buildings, expand parking and make road and other campus improvements. It added that the "continued support and action by state and local governments will be required".

Nike at the end of last year committed to an expansion of its operations in Oregon, that could lead to the creation of 500 jobs and US$150m in capital investment over five years. The company expects to begin construction later this year.

"Nike is a growth company with a long history in Oregon and we look forward to continuing to grow here," said Nike president and CEO Mark Parker.

Washington County is home to more than 8,000 Nike employees and contract workers. Since 2007, Nike said its employment in Oregon has grown by nearly 60%.