(AFP) -

President Barack Obama on Thursday ordered federal employees not to send text messages while driving as his administration pressed a campaign against the dangers of distracted driving.

An executive order signed by Obama said the federal government's three million civilian employees "shall not engage in text messaging" while driving official vehicles or while driving their own vehicles on official business.

The order "sends a very clear signal to the American public that distracted driving is dangerous and unacceptable," Transportation Secretary Ray LaHood said at the close of a two-day meeting on the issue.

Last year nearly 6,000 people were killed and more than half a million injured in the United States in accidents attributable to "distracted driving."

LaHood said the Department of Transportation was toughening up rules put in place last year to limit texting and mobile phone use in the freight and passenger rail industries.

New restrictions will prohibit text messaging by bus drivers who travel between states and by truck drivers. School bus drivers convicted of sending a text message while driving would be stripped of their commercial drivers' licences.

The transportation chief also called on state officials to pass laws against distracted driving.

"High-visibility enforcement has proven effective in reducing drunk driving and increasing seatbelt use. We believe it can also work for distracted driving," LaHood said.

Currently, only six states -- California, Connecticut, New Jersey, New York, Oregon and Washington plus Washington DC -- have laws banning the use of handheld phones while driving.

Eighteen states and the District of Columbia have banned drivers from sending text messages while at the wheel.