WASHINGTON (Reuters) - The U.S. Food and Drug Administration is “pushing very hard” to release a proposed rule that would establish its authority over e-cigarettes, the head of the agency said on Thursday amid concerns the products pose a risk to children.

Various e-cigarette products for sale are seen at the Henley Vaporium in New York City December 18, 2013. REUTERS/Mike Segar

FDA Commissioner Margaret Hamburg told senators at a Congressional budget hearing that it has taken too long to move the rule forward and that she expects the proposal to be ready for release “very soon.”

The FDA’s proposal is currently being examined by the White House’s Office of Management and Budget, which reviews potential regulations to assess their economic impact. OMB, which has been reviewing the proposal for roughly five months, has not said when it will be finished with its assessment.

A growing chorus of public health advocates and lawmakers are pressing for prompt release of the proposal, arguing that the delay presents risks to children who may be attracted to the sweet flavors often contained in e-cigarettes.

Senator Jeff Merkley, Democrat of Oregon, told Hamburg that the agency’s delays were “disgraceful” since makers of products such as tutti-frutti flavored e-cigarettes and strawberry-flavored cigars have “an insidious strategy to addict our children to nicotine.”

“Four years and four months to get the first draft over to OMB is unacceptable,” he said. For OMB to sit on it for months, he added, “is unacceptable.”

Hamburg said the criticisms were fair.

“I do believe that very soon I will be able to call you, and say the deeming rule is out,” she said.

A law passed in 2009 gave the FDA the authority to regulate cigarettes, smokeless tobacco and roll-your-own tobacco. It also gave the agency the power to “deem” other tobacco products to be within its jurisdiction but it must first issue a rule to that effect.

E-cigarette companies believe they should be exempt from the full spectrum of regulations, saying they would stifle innovation, damage small business and hurt consumers trying to quit smoking.

Hamburg also responded to concerns about an apparent rise in the number of poisoning cases from liquid nicotine, the substance contained in e-cigarettes that, when heated, forms an inhalable vapor.

On Thursday a report from the Centers for Disease Control and Prevention showed that the number of calls to poison centers involving e-cigarette liquids containing nicotine rose from one per month in September 2010 to 215 per month in February 2014. The number of calls per month involving conventional cigarettes did not show a similar increase, the report said.

“We do feel that this in an area that requires greater attention, action and concern,” Hamburg said.