By alley - Apr 30, 2016, 1:08 PM ET

INDYCAR: Shank keeping 500 window open

Michael Shank isn't ready to pull the plug on entering a car for next month's Indy 500, but he does admit the chances have grown slim.

The veteran open-wheel and sports car team owner is known to have been working on a Honda-powered program using a spare chassis from Bryan Herta Autosport to field 2015 Indy 500 Rookie of the Year Gabby Chaves. Shank set a Friday night deadline for the deal to be completed.

"The deal I was fighting for isn't going to happen with [Gabby], but I'm keeping the window open in case something comes together," Shank told RACER. "I'm not giving up, but it isn't looking as optimistic as it did earlier in the week."

Thirty-four entries have been confirmed

for the 100th running of the "Greatest Spectacle in Racing," and more could be on the way. Grace Autosport has been busy assembling the pieces to become the 35th entry, and if Shank's deal makes a quick turnaround, the number could reach 36.