Michelle Obama looked unimpressed during the inauguration of Donald Trump as 45th President of the United States – summing up the mood among critics of the controversial billionaire who was sworn in at a ceremony on Capitol Hill.

Eyebrow raised, the former first lady stood and watched as Mr Trump recited the 35-word oath.

Her dour facial expression prompted an immediate reaction on social media, with one person saying that her evident displeasure at the New York tycoon becoming the most powerful man on the planet “spoke for all of us”.

U.S. President Donald Trump shakes hands with outgoing U.S. Vice President Joe Biden as outgoing President Barack Obama and Michelle Obama look on (Reuters)

One image showed Ms Obama – who has been touted as a future presidential candidate – standing uncomfortably as she gave the new US President a sideways glance.

She also appeared unimpressed earlier in the day when she was handed a box by Mr Trump’s wife Melania.

Ms Obama looks around for somewhere to put the ribbon-wrapped box, before shooting a swift look of desperation at the camera (screen grab)

The outgoing first lady grimaced as she turned to the waiting photographers clutching the box, which is said to be from the jewellery shop Tiffany, which neighbours Trump Tower on Fifth Avenue.

Hillary Clinton and husband Bill were also among the gathered dignitaries. The defeated Democratic nominee appeared steely-eyed as she awaited Mr Trump's arrival.

But more than 60 fellow Democrats refused to attend his swearing in ceremony, which saw Mr Trump placing his hand on two Bibles, one used by his family and another used for President Abraham Lincoln's inauguration.

The new US President declared a united America was “totally unstoppable” and said the country would “start winning again, winning like never before”.

Donald Trump mimics Obama as they walk out of White House