The All Blacks Sevens and Black Ferns Sevens squads headed to the 2018 Rugby World Cup Sevens have been named. 

Both teams will look to defend their world cup titles, under a new knock-out format, at the San Francisco tournament in ten days' time.

Black Ferns Sevens coach Allan Bunting says selecting the newly named squads was not easy. 

"It was the hardest squad to pick since I've been involved in this whole programme. All our players competing are fast, fit and beating each other on the field in the last couple of weeks."

Newcomer Black Fern to the World Cup Stacey Waaka says everyone put in the hard yards, vying for spots and she was fortunate that she made it in the Black Ferns team.

"It's been amazing it's always been a dream of mine. Comm Games was cool but the World Cup is obviously the pinnacle of sevens so extremely excited."

The stakes are high for both defending World Cup champions with the new knock-out format equalising the playing field for the 16 national unions for the women's and 24 countries in the men's tournaments.

Portia Woodman is one of four women's players returning to the World Cup and says the rest of the squad has just as must experience. 

"We've also got girls who have been to Rio Olympics to a Comm Games and played in every single tournament after that so we've got a lot of experience in our team and I trust those heaps."

Both teams will play their first match of the World Cup on Saturday July 21.