(Jan 20): Incoming US first lady Melania Trump stepped out in a Ralph Lauren baby-blue jacket and matching dress on Friday, choosing one of America's most iconic designers for Inauguration Day ceremonies.

The former fashion model's custom-designed Ralph Lauren outfit, worn with long matching gloves and stiletto shoes, had a 1960s vibe and wowed fashionistas.

Womens Wear Daily said the outfit, with its mock turtle neck, triggered comparisons to the late US first lady and style icon Jacqueline Kennedy.

Style-watchers agreed, posting archive photos of Kennedy in a similar blue outfit for her husband's inauguration in 1961, and giving Trump's outfit a large thumbs-up.

"It was very Jackie," said Joe Zee, editor in chief of Yahoo Style.

"Melania looks every inch a First Lady. So beautiful and classy! I'm proud of her!," Theodora West wrote on Twitter.

Melania Trump's Inauguration Day outfit had been the cause of much speculation after Tom Ford, Marc Jacobs and other leading designers said publicly they would not dress the first lady for her big day because they opposed her husband, Donald Trump.

New York-born designer Lauren, however, was the designer behind Melania Trump's election night white jumpsuit.

Ironically, Lauren was also the designer of the pantsuits in many colors that became Democratic presidential contender Hillary Clinton's signature look.

Lauren and his eponymous corporation became synonymous with American style through his preppy line of Polo shirts, casual slacks and shorts in the 1970s and is regarded as one of the most influential designers of the 20th century.

Melania Trump, 46, is the first US first lady to come from the fashion world. She began life as a teen model in her native Slovenia and has been featured on the cover of magazines like Vogue and GQ.

Standing 5 feet, 11 inches (1.8 meters) tall, she tends to favour unfussy dresses in solid colors, tailored coats and killer high heels.