Fernando Alonso admitted it had been a "difficult week" after narrowly failing to qualify for the Indianapolis 500, denying him the chance to complete motorsport's Triple Crown.

Having already achieved victories in the Monaco Grand Prix and Le Mans 24 Hour, the two-time Formula One champion was hoping to add the Indy 500 title to his collection, but will now have to wait to match the accomplishment of the late Graham Hill.

Alonso was 31st fastest on Saturday and went into Sunday with a new set-up in the hope of grabbing one of the final three spots for the annual 200-lap, 500-mile race next Sunday.

The McLaren driver's 227.353mph four-lap average saw him bumped from the grid when Kyle Kaiser went just 0.019mph faster with the last run to make up the 33-strong qualifying pack.

Writing on Instagram, Alonso said: "A difficult week, no doubts. We tried our best, even today with a completely different set up and approach, 4 laps flat on the throttle but we were not fast enough.

"It's never easy to drive around here at 227mph +, and want more speed... We tried our best and we've been brave at times, but there were people doing better job than us.

"Success or disappointments only come if you accept big challenges. We accepted. Thanks to the massive support always here at the speedway and everyone at home. Now full focus on next target."

McLaren also conceded it had been a tough week.

"We're hugely disappointed not to make it through to next Sunday's 2019 #Indy500. It's been a tough week for the team. We're sorry that our fans didn't get the chance to cheer us on at the Brickyard, but thank you all so much for your support. #McLaren66," they tweeted.

Frenchman Simon Pagenaud (Team Penske) took pole position with an average speed of 229.992mph.

Motorsport's unofficial Triple Crown consist of wins at the Indy, Le Mans and the Monaco Grand Prix.

Alonso enjoyed victory with Toyota Gazoo Racing at Le Mans in 2018 and won twice at Monaco before leaving Formula One last season.