Image caption US government health officials say pupils should have more diverse diets

The US Senate has blocked a proposal by the Obama administration to limit potatoes in school lunches.

The lawmakers also backed an amendment which bars putting any limits on serving other vegetables in US schools.

The administration's proposal had envisaged that pupils would have no more than two servings a week of potatoes and other starchy vegetables.

Government health officials say pupils should have more diverse diets, because they get enough potatoes already.

But opponents of the proposal argue that potatoes can be a source of fibre and potassium.

They also say that potatoes and other vegetables are a cheaper and nutritious way to feed children when schools are strapped for cash.

"This proposed rule would have imposed significant and needless costs on our nation's school districts at a time when they can least afford it," Susan Collins, a Republican senator from Maine, was quoted as saying by the Associated Press news agency.