By Alan Baldwin

LONDON (Reuters) - The competition for the last three slots on the 2017 Formula One starting grid is hotting up but Indonesian driver Rio Haryanto believes he is still in with a shout.

"Of course there is a chance to get back again. We are working hard to get the seat back," the 23-year-old told Reuters. "It has to be next year."

Haryanto started 12 races for Manor this year, becoming the first Indonesian to compete in Formula One, before being replaced by French rookie Esteban Ocon after the German Grand Prix in July.

He has been the team's reserve since then, itching to get back on the racetrack.

Manor's future is currently up in the air, with owner Stephen Fitzpatrick saying at last weekend's Abu Dhabi Grand Prix that talks were at an advanced stage with an unnamed investor, and they have yet to confirm their two drivers.

The other seat still open is at Sauber.

Ocon has already moved on to Force India for 2017 while Germany's Pascal Wehrlein, the Mercedes reserve who raced for Manor this year, has been linked to Sauber in media speculation if he does not stay at his current team.

Brazilian Felipe Nasr and Mexican Esteban Gutierrez are also seeking to secure their Formula One futures and talking to Manor.

Nasr has lost a key sponsor in Banco do Brasil, which makes staying at Sauber uncertain, while Gutierrez has been replaced at Haas by Denmark's Kevin Magnussen after failing to score a point all year.

Haryanto's manager Piers Hunnisett told Reuters that he was doing all he could in the "game of musical chairs".

"There are three places left now. Once one gets done, everything else can go very quickly. We are just watching everybody," he said.

"I’m quite positive we can do something. But things change very quickly in Formula One. I know we’ve still got huge support from Indonesia, the media and the fans. Sponsorship is ongoing," he added.

Hunisett said his focus was now more on private backers across South-East Asia rather than government funding, although Haryanto could count on ongoing support from state oil and gas company Pertamina.

"When it comes to releasing the money, when you’ve got housing problems and education and health issues, it is difficult to justify," he said of state support.

"We have got some more leads now with other sponsors, non-government, where it’s easier to work with.

"The good thing is that Rio is the only driver from Asia, so from a marketing point of view...up until Germany, we were just starting to make inroads into other markets -- China, Thailand, Malaysia. The interest was growing."

(Reporting by Alan Baldwin, editing by Toby Davis)