The small US state of Connecticut became the first to pass legislation requiring food products with genetically modified ingredients to be labeled as such.
But the law, passed on Monday, will not go into effect until a number of other states in the northeastern region where Connecticut is located follow suit with similar legislation.
The legislation was strongly supported in a 134-3 vote in the state House of Representatives, making Connecticut the first of some two dozen states mulling GM foods labeling to pass a measure.
The bill had been passed by the Senate on Saturday.
The state's governor, Dannel Malloy, endorsed the legislation ahead of the vote, saying it "strikes an important balance by ensuring the consumers' right to know what is in their food while shielding our small businesses from liability that could leave them at a competitive disadvantage."
With just 3.6 million people in the state, it was necessary to tie enactment of the law with other states doing the same.
The bill said that the labeling rules will only take effect when at least four other states, including at least one of them an immediate neighbor of Connecticut such as New York, enact similar legislation, and also only when states in the northeastern region of the country with a combined population of 20 million or more do the same.
"Connecticut is a fairly small state and we wanted to make sure that it wouldn't be the only state in the region to pass such a law, which could have been a disadvantage for our small businesses," said Todd Murphy, a spokesman for the House of Representatives.
Officials had stressed that it was only an issue of informing consumers and that no restrictions were placed on GM ingredients under the new law.
The Center for Food Safety, which campaigns against GM foods—also known as genetically engineered (GE) foods—applauded the vote.
"Numerous other states in the Northeast and around the country are actively considering pending GE food labeling bills," said the center's Rebecca Spector in a statement.
"Connecticut's leadership provides momentum and an incentive for these other states to move forward."