A US biotech company says it plans to start this summer the world's first study of a treatment based on human embryonic stem cells - a long-awaited project aimed at spinal cord injury.

The company gained federal permission this week to inject eight to 10 patients with cells derived from embryonic cells, said Dr Thomas Okarma, president and CEO of Geron Corp. of Menlo Park, Calif.

The patients will be paraplegics, who can use their arms but can't walk. They will receive a single injection within two weeks of their injury.