Hartley, 27, has been part of Porsche's LMP1 program since its inception in 2014, and won the WEC title the following year with teammates Mark Webber and Timo Bernhard.

After taking victory in this year's Le Mans 24 Hours alongside Bernhard and Earl Bamber, the trio are firmly on course to seal this year's championship following a fourth successive race win last weekend at Austin.

But, the announcement that Porsche is to exit LMP1 at the end of the year in favor of a Formula E entry in 2018/19 has left Hartley having to seek a drive elsewhere for 2018.

The Kiwi recently tested a Venturi Formula E car, but has also been strongly linked to an IndyCar move. After appearing on the Schmidt Peterson Motorsports radar, there are strong rumors he's at the top of Chip Ganassi's list of potential replacements for Tony Kanaan.

"I'm not sure what I'm going to be racing next year, I'm looking at a lot of different options," Hartley told Motorsport.com in Austin.

"For the moment nothing's clear, but I'm confident I'll be a in a good place next year. I spoke to many different teams [in Formula E], I tested with Venturi, but I've also been speaking to IndyCar teams, IMSA teams.

"I'd love to be in IndyCar and hopefully in the next weeks something will become clear. I'm genuinely looking closely at IndyCar and it would be a new challenge.

"I'm excited about the challenge of the ovals if IndyCar comes to fruition."

Ongoing Porsche links

Hartley added he expects to maintain his relationship with Porsche wherever he ends up racing next season, possibly incorporating some GT races with the Weissach marque.

"The plan is wherever I go next year I'll still have some kind of relationship with Porsche and we'll hopefully still compete in a few races," he said.

"But with LMP1 stopping, there are going to be a lot of drivers [available] and not enough races for a full-time ride."

Hartley has also confirmed on social media he will rejoin Tequila Patron ESM for IMSA's Petit Le Mans season finale, following on from his appearances in the Daytona 24 Hours and Sebring 12 Hours this year.

Additional reporting by Kunihiko Akai