Tomas Berdych and Jo-Wilfried Tsonga have confirmed that they will join Andy Murray in competing at the Queen's Club in June.
As it stands, world number six Berdych is the highest-ranked player to have accepted the invitation to play in the warm-up event in London, although Murray could leapfrog the Czech Republic number one by collecting positive results over the next six weeks.
Marin Cilic, whom Murray defeated to win the title 12 months ago, will also be present, as will Leyton Hewitt, Grigor Dimitrov and Kevin Anderson.
This year's tournament will be directed by Ross Hutchins.