Megan Rapinoe has embraced a different role for the United States as the decorated veteran bids to bow out from the World Cup with a third title in a row.

The 38-year-old is set to retire from football at the end of the season and is the senior member of a US squad packed with young talent in Australia and New Zealand.

The forward scored six goals, earning both the Golden Ball and Golden Boot, as the Americans triumphed once more in France four years ago.

Her open-armed goal celebration became a defining image of the tournament.

Rapinoe is just as formidable off the field. she was a key voice in the team's battle with the US federation for equal pay and conditions, and remains an unflinching advocate for women and the LGBTQ community.

She is now past her prime on the pitch and won't play every minute at her fourth World Cup, but US coach Vlatko Andonovski said the 2019 Ballon d'Or winner was as important as ever.

"First and foremost, the thing with 'Pinoe' is, when she's on the field, she's a great player," he said in the build-up to the tournament.

"That's the first reason why she's on this team.

"She's one of the most creative players that I've ever seen."

Rapinoe's experience and leadership will arguably be just as critical off the field for a squad that features 14 World Cup newcomers.

"She will have a role of a player-leader -- and leading the leaders as well," Andonovski said.

The United States begin their campaign on Saturday when they face Vietnam in Auckland and are favourites to retain their crown over the next month.

Setting the standard

Rapinoe took a knock in a June 10 game for her club OL Reign in the National Women's Soccer League but expects to be fit for whenever she is needed.

"It was quite minor," she said. "Not amazing timing, but such is life for an athlete. It's nothing I'm worried about for the start of the tournament."

Whatever minutes she ends up playing, Rapinoe still sets the standard for the rest of the World Cup squad.

"First, she's an amazing player, so on the field you already know where the level needs to be," said 18-year-old forward Alyssa Thompson.

"And off the field she's so funny and makes me feel comfortable even though I'm so young and she's much older than me.

"She just makes me feel like I'm supposed to be here too."

Rapinoe certainly doesn't need anyone to make her feel she belongs at a World Cup, but nor has she lost her sense of wonder at taking part in what she calls "the premier women's sporting event in the world, bar none."

"I can't believe we're back at the World Cup again," she said. "This is the best moment of all our career.

"It never gets old."