The decision by the Federal Aviation Administration follows the announcement by two Japanese airlines that they have grounded all of their 787s after a sixth problem with the aircraft in less than two weeks.
The planes will be grounded until the risk of possible battery fires is addressed, the US official has said.
The federal agency plans to work with Boeing on a plan to allow the Dreamliners to "resume operations as quickly and safely as possible".
European safety regulators said they would follow the US in ordering the grounding of 787s amid concerns over battery safety.
The European Aviation Safety Agency (EASA) typically implements safety directives when they are issued by the country where the aircraft was originally designed - in this case the US.
A spokesman for EASA said: "In this case, we have issued no airworthiness directive so far, so the FAA's directive should be endorsed by EASA."
United Airlines is the only American carrier to have 787s and has six of the aircraft in its fleet.
The decision comes just days after the FAA Administrator Michael Huerta and Transport Secretary Ray LaHood declared the plane safe.
All Nippon Airlines (ANA) announced it was grounding all 17 of its 787s after one was forced to make an emergency landing in west Japan on Wednesday.
Japan Air Lines Co Ltd (JAL) said it would also suspend all Dreamliner flights scheduled to leave Japan on Wednesday over safety concerns.
Public broadcaster NHK said the ANA aircraft landed in Takamatsu and all passengers on board were evacuated after smoke was seen in the cabin.
ANA spokeswoman Naoko Yamamoto said: "It made an emergency landing at Takamatsu because there was an error message during the flight.
"It is true that the aircraft has recently seen a series of troubles. But we cannot say if this has something in common with previous problems."
A statement later said a battery problem had forced the emergency landing.
TV footage showed emergency chutes deployed from the plane at the airport, on Japan's fourth largest island of Shikoku.
ANA said 129 passengers and eight crew were on board. Some of the passengers were reported to have suffered minor injuries as the plane was evacuated.
The aircraft was travelling to Haneda Airport in Tokyo.
On Friday, oil was discovered leaking from another ANA operated Dreamliner at Miyazaki airport in southern Japan.
On the same day, a cracked cockpit window was also discovered on another of its 787s.
Last Wednesday, a domestic flight was halted by ANA because brake parts to the rear left undercarriage needed replacing.
And a JAL jet was also grounded at Boston Logan International airport in the US following an engine fuel leak.
Another JAL 787 filled with smoke shortly after passengers and crew had disembarked last Monday.
Japanese authorities announced on Monday they would investigate the fuel leak.
Japan is the biggest market so far for the Dreamliner, with ANA and Japan Airlines Co flying 24 of the 50 Dreamliners delivered to date.
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