US First Lady Michelle Obama stayed loyal to Jason Wu on Monday, choosing the Taiwan-born, New York-based designer for her much-anticipated inaugural ball dress as she did four years ago.

She appeared before a cheering crowd of thousands in Washington's cavernous convention center in the ruby-colored, halter-top chiffon and velvet gown by Wu, with Jimmy Choo shoes and a Kimberly McDonald diamond-embellished ring.

President Barack Obama, in a sharp tuxedo, held her close as they slow-danced on stage to pop songstress Jennifer Hudson covering Al Green's soul classic "Let's Stay Together."

"Just danced to 'Let's Stay Together' with the love of my life and the President of the United States," the first lady said on Twitter. "I'm so proud of Barack."

Wu, who dressed Obama in a one-shouldered white gown for her first inaugural balls in 2009, told the fashion trade journal Women's Wear Daily that he was floored to see her pick one of his custom creations once again.

"Mrs. Obama likes to keep her secrets. She fooled me again," he told WWD.

Earlier in the day, for Obama's public oath-taking on the steps of the Capitol, the first lady bundled up against the near-freezing temperatures in a navy Thom Browne coat and dress with a J.Crew belt and gloves.