A New York judge blocked mayor Michael Bloomberg's planned ban on giant sodas Monday, dealing a setback to his public health agenda just hours before curbs on selling such drinks were due to begin.

Judge Milton Tingling ruled that measures to restrict soda servings to a maximum of 16 ounces (470 milliliters) in restaurants and other venues, were "arbitrary and capricious," and he was barring the plan "permanently."

Bloomberg has made health issues a key plank of his administration, banning smoking in restaurants, bars and other public places. He quickly denounced the judge's decision on sodas as "clearly wrong," and said the city would appeal.

"I am trying to do what is right to save lives. Obesity kills," a visibly angry Bloomberg told reporters, noting that 5,000 New Yorkers and 70,000 US citizens would fall victim to the disease this year.

"Sugary drinks are a leading cause of obesity. We have a responsibility as human beings to do something, to save each other," he added.

But Bloomberg's super-sized soda ban, which would have been a first for a US city, sparked frenzied debate, with petitions and media campaigns from both sides.

Some supported Bloomberg's arguments, emphasizing that 30 years ago the average soda serving was just six ounces, but that these days, it's not rare to see young Americans with giant fizzy drinks of more than a liter (33 ounces).

Opinion polls over the summer indicated that a majority of New Yorkers opposed the limited ban, with some suggesting the mayor was impinging on civil liberties and others arguing the rules would not be effective.

Industry lobby groups led by the American Beverage Association (ABA) and the National Restaurant Association took the court action that led to Monday's judgment, and they praised the decision.

"The court ruling provides a sigh of relief to New Yorkers and thousands of small businesses in New York City that would have been harmed by this arbitrary and unpopular ban," the ABA said in a statement.

As well as the thousands who die each year from obesity-linked problems, one in eight adult New Yorkers has diabetes, which can be aggravated by sugar consumption, and studies have shown that sodas, which often cost less than bottled water, are a contributing factor.

"Remember, for many years, the standard soda size was six ounces -- not 16, it was six, then it was 12 ounces -- and people thought that was huge. Then it became 16, then 20 ounces," Bloomberg said.

"We believe it's reasonable to draw a line -- and it's responsible to draw a line right now," he added.

The New York Board of Health approved the measures last September and they were due to come into force on Tuesday in restaurants and places of public entertainment, such as stadiums.

In a boost for the soda limits, the newly-built basketball stadium for the Brooklyn Nets had said it would immediately adopt the rules.

But under the measures put forward by the city there was nothing to stop people from buying as much soda as they like by refilling smaller containers.

Also, the ban did not extend to drinks sold in supermarkets or any dairy or fruit drinks, many of which also contain huge quantities of sugar.

Diet and alcoholic drinks were also exempted under the city's plan.

"The exclusion of all alcoholic beverages from the ban is completely irrational. Beer and soda have nearly the same calories per ounce," the legal complaint said.

And "the application of the ban to some business establishments but not others is arbitrary and capricious," it argued.

Bloomberg previously acknowledged that the plan would fall short of ending over-consumption of sugary drinks, but he said the disappearance of mega-sized cups would at least make people more aware of what they were consuming.