The success of Auckland at the NHL helped King force her claims.
"It is a huge honour to be selected. I'm looking forward to training with the team and competing at that level," said King.
"You learn so much from the Black Sticks about their work ethic and from their individual play, it is all very exciting,"
Dennison, 18, is completing her final year by correspondence having recently left Rangitoto College to focus on hockey. She said the coaching and support she has received from North Harbour coaches and ex Black Sticks Bryce Collins and Dave Kosoof has been a huge help.
"I'm looking forward to learning more about hockey," said Dennison.
"Being able to develop my skills and having my play analysed by the national coaches, that will really help me improve my game. It is such a huge opportunity."
With long-serving goalkeeper Bianca Russell sidelined with a knee injury, youngster Amelia Gibson gets her chance to join Sally Rutherford as the two goalkeepers in this squad which leaves for the US on August 30 - the day after Hager and Black Sticks men's coach Shane McLeod will name their Olympic squads.
Both teams will head to Tasmania for October's Oceania Cup where a second-place finish will confirm their places at the London Olympics.
Fiji will join New Zealand and Australia at that tournament.
While the women will then take a break, a 20-strong New Zealand under-21 team will head to India in November.
In late January-early February the women will play the Champions Trophy in Argentina after which the squad will be centralised in Auckland.
Black Sticks squad:
Kayla Sharland, Emily Naylor (Central), Krystal Forgesson, Jan Burrows, Katie Glynn, Lucy Talbot, Sam Harrison, Julia King (Auckland), Sally Rutherford, Samantha Charlton, Cathryn Finlayson, Gemma Flynn (Midlands), Amelia Gibson, Sophie Devine (Canterbury), Ella Gunson, Charlotte Harrison, Stacey Michelsen (Northland), Anita Punt (Wellington), Rhiannon Dennison (North Harbour)