As part of its recommendation, the National Transportation Safety Board is urging states to ban drivers from using hands-free devices, including wireless headsets. No state now outlaws such activity, but the board said that drivers faced serious risks from talking on wireless headsets, just as they do by taking a hand off the wheel to hold a phone to their ear.

And Deborah Hersman, chairwoman of the N.T.S.B., an independent federal agency responsible for promoting traffic safety and investigating accidents, said the concern was heightened by increasingly powerful phones that people can use to e-mail, watch movies and play games.

“Every year, new devices are being released,” she said. “People are tempted to update their Facebook page, they are tempted to tweet, as if sitting at a desk. But they are driving a car.”

The agency based its recommendation on evidence from its investigation of numerous crashes in which electronic distraction was a major contributing factor.

Ms. Hersman said she understood that this recommendation would be unwelcome in some circles, given the number of drivers who talk and text. But she compared distracted driving to drunken driving and even smoking, which required wholesale cultural shifts to change behavior.

“It’s going to be very unpopular with some people,” she said. “We’re not here to win a popularity contest. We’re here to do the right thing. This is a difficult recommendation, but it’s the right recommendation and it’s time.”

The agency’s recommendation is nonbinding, meaning that states are not required to adopt such a ban. And it will likely be frowned upon by state lawmakers makers who are loath to infuriate constituents who have grown accustomed to using their device behind the wheel.

But, the recommendation may also provide cover for legislators, safety advocates and others who support such a broad-based ban. Many polls show that while people continue to use their devices behind the wheel, they also widely consider such behavior to be extremely dangerous.

The ban is also noteworthy because it is the first call by a federal agency to end the practice completely, rather than the partial ban that some legislators have put in place by allowing hands-free talking.

State Senator Joe Simitian of California, who succeeded in getting a law passed in 2006 that bans drivers there from talking on a hand-held phone, called the board’s recommendation “a wake-up call about the dangers of distracted driving.”

Yet, he also said he doubted it would achieve the desired result because it was unlikely that legislators in California or elsewhere would be able to pass such a ban. Mr. Simitian noted that he spent five years trying to push a ban on hand-held devices, and faced intense opposition from the phone industry.

“It’s a political nonstarter,” he said, adding that he would not attempt to propose a total ban on drivers using their devices. “I don’t believe you’ll see such a ban in my lifetime.” For all his skepticism, though, he acknowledged that political winds could shift. “A decade ago, people didn’t think we’d have a hands-free law in California. Only time will tell.”

Nine states now ban the use of hand-held phones, and 35 states ban texting by drivers, according to the Governors Highway Safety Association, which represents state traffic agencies. The group’s executive director, Barbara Harsha, called the N.T.S.B. recommendation “courageous” and said it would prompt the group to reconsider its policy, which calls for banning drivers from texting but not talking on the phone.

“People may not be ready for that,” she said of such a ban. “But there will certainly be discussion about it.”

Many mobile phone companies dropped their opposition over the last decade to any restrictions on the use of phones in cars, and have in recent years joined calls to ban texting while driving. In a statement,CTIA, the cellular telephone industry trade group, said it deferred to states about whether to enforce such bans.

A complete ban on phone use by drivers would have enormous impact on many car makers that are offering integrated hands-free, voice-activated systems that allow drivers to talk and do other tasks, like calling up their phone directory.

The Alliance for Automobile Manufacturers, a trade group for the industry, said in a statement that it was reviewing the N.T.S.B. recommendations. But it also defended the integrated systems, saying they allow drivers to keep their hands on the wheel and eyes on the road while they remain connected.

“What we do know is that digital technology has created a connected culture in the United States and it’s forever changed our society:  consumers always expect to have access to technology; so managing technology is the solution,” the alliance said in a statement.

Ms. Hersman, the chairwoman of the N.T.S.B., said the safety concerns were not just about keeping hands on the wheel and eyes on the road, but also about making sure people focus on the act of driving.

“It’s about cognitive distraction. It’s about not being engaged at the task at hand,” she said, adding: “Lives are being lost in the blink of an eye. You can’t take it back, you can’t have a do over, and you can’t rewind.”

The issue is gaining greater internationally, too.

Last year, Ban Ki-moon, secretary general of the United Nations, called for an end to the culture of multitasking behind the wheel. Already, 30 countries have some limitations on the use of phones by drivers, including complete bans in Germany and Portugal, said Bella Dinh-Zarr, road safety director of international road safety with theFIA Foundation, a road safety advocacy group.

Because of the growing research and concern about the issue, she said, “More and more countries are going to be looking at it.”