Michelle Obama is the belle of ballet... but has stiff competition from Renee Zellweger in the toned arm department

Michelle Obama may have it all her own way in Washington with her sleek physique and super-toned arms.

But the celebrities came out in force at the launch of the American Ballet Theatre’s Spring Gala, and there were plenty of highly-toned Hollywood biceps on show.

Actress Renee Zellweger in particular gave the First Lady some stiff competition in the sinewy arm department as she posed and preened in a strapless ballgown at last night’s event at the Metropolitan Opera House in New York.

First lady Michelle Obama spent her second New York City visit reopening part of the American wing of the Metropolitan Museum of Art and later addressing the crowd at a glittering ballet gala.

In a sleeveless black Azzedine Alaia gown and Thakoon jacket, Mrs Obama, 45, showed off her marvellous gym-honed arms.

While Renee, 40, showed off her arms, in a grey gown which swamped her tiny frame. But as glamorous as her attire was, she let herself down somewhat with the lack of attention to her hair.

Mrs Obama and Renee were also joined by Sigourney Weaver, 59,  and Vogue editor Anna Wintour, 59, model Iman, 53, actress Claire Danes, 30, and Lynda Carter, 57.

Interestingly, Somali-born model Iman, one of the first black supermodels, recently told Parade magazine: ‘Mrs Obama is not a great beauty. But she is so interesting looking and so bright. That will always take you farther.

‘When you’re a great beauty, it’s always downhill for you. If you’re someone like Mrs Obama, you just get better with age.’ Clearly, they would have had plenty to talk about.

Earlier in the day the First Lady cut the ribbon for the newly renovated American wing of New York’s Metropolitan Museum of Art wearing a stunning amethyst Isaac Mizrahi shift dress and matching coat.

She said: ‘The arts are not just a nice thing to have or to do if there is free time or if one can afford it.

Look at me: Iman chose a juicy lime green gown which showcased her bingo wingless arms too

‘Rather, paintings and poetry, music and fashion, design and dialogue, they all define who we are as a people and provide an account of our history for the next generation.’

The First Lady said she and the president hope to give America’s children better access to the arts and the ability to turn their artistic talents into careers.

To the amusement of a crowd that included Mayor Michael Bloomberg, Sen. Kirsten Gillibrand, Vogue editor Anna Wintour, former model Iman and designer Ralph Lauren, Mrs. Obama was reminded by museum president Emily Rafferty that she and the president had their first date in a museum.

‘Thank you for reminding me,’ Mrs. Obama said.

‘You know, after 20-some-odd years of knowing a guy, you forget that your first date was at a museum. But it was obviously wonderful; it worked.’

Not competing: Actress Sigourney Weaver of Aliens fame covered up on arrival in a fake fur coat

The American Ballet Theatre’s opening night gala kicked off the Company’s eight week season at the Metropolitan Opera House and featured the company’s principal dancers in highlights from the season.