WASHINGTON — A slice of pizza still counts as a vegetable.

In a victory for the makers of frozen pizzas, tomato paste and French fries, Congress on Monday blocked rules proposed by the Agriculture Department that would have overhauled the nation’s school lunch program.

The proposed changes — the first in 15 years to the $11 billion school lunch program — were meant to reduce childhood obesity by adding more fruits and green vegetables to lunch menus, Agriculture Department officials said.

The rules, proposed last January, would have cut the amount of potatoes served and would have changed the way schools received credit for serving vegetables by continuing to count tomato paste on a slice of pizza only if more than a quarter-cup of it was used. The rules would have also halved the amount of sodium in school meals over the next 10 years.

But late Monday, lawmakers drafting a House and Senate compromise for the agriculture spending bill blocked the department from using money to carry out any of the proposed rules.