Fernando Alonso has lost another option to run in this year's Indianapolis 500 after Ed Carpenter ruled out adding a seat.

The Spaniard is hoping for a third attempt at IndyCar's premier event in 2020 as he bids to become the second driver in history to complete motorsport's Triple Crown.

However, a deal agreed with Andretti Autosport was blocked by engine supplier Honda, leaving Alonso scouring only Chevrolet-powered teams for a ride.

“There is one person that has reached out to me about it, but it wasn’t Alonso or anybody that works for him," Carpenter, IndyCar's only team owner/driver told NBC Sports.

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"It’s been surprisingly quiet. I think it’s because they know we are not positioned to run more than three. We are a two-car team.

“If we doubled the size of our team for May, it wouldn’t be good for everybody.”

His decision reduces Alonso to four teams, including McLaren's new full-time IndyCar outfit, Arrow McLaren SP, and Carpenter admits he doesn't understand why the two-time Formula 1 champion didn't see Honda's intervention coming, given their history.

"It had happened before,” said Carpenter.

“The difference is Fernando is separated from McLaren. It was pretty surprising they got that far down the road before they realized it was going to become an issue with how public that dispute had become.”