The United States Food and Drug Administration (FDA) has approved Golden Rice, the fourth country to give a thumbs-up to a rice strain genetically altered to prevent blindness in children.
The rice contains extra genes that make a precursor to vitamin A, which is vital for preventing childhood blindness.
A single helping can supply half the recommended daily intake of vitamin A, according to its developers at the International Rice Research Institute in the Philippines. The genes also give it a distinctive golden hue.
In February and March, Food Standards Australia, New Zealand and Health Canada gave Golden Rice the stamp of approval.
"Based on the information IRRI has presented to FDA, we have no further questions concerning human or animal food derived from GR2E rice at this time," the US FDA's letter to IRRI concludes.
The rice is intended to address Vitamin A deficiency (VAD), a serious disease which is estimated to affect 250 million preschool-age children around the world. VAD can cause blindness and early death in young children who are affected.
Its developer says the most important approvals are still awaited in the Philippines and Bangladesh, where the rice could have the greatest impact.
Applications were lodged in these countries last year.
Greenpeace has opposed development and approval of golden rice, controversially claiming that it does not benefit farmers, only commercial enterprises.
The IRRI has replied that farmers or any consumers are allowed to plant and replant this crop as long as they don't exceed the equivalent of 320,000 baht in profits. Farmers are also allowed to keep the seeds and replant them. Licences from the IRRI are free.