File picture: Paulo Whitaker / Reuters.

Sao Paulo - Interlagos served up a tense and lively thriller on Sunday but the long-term future of the Brazilian Formula One Grand Prix remains uncertain.

The existing contract expires in 2020 and negotiations, difficult in the past due to demands for costly improvements of the atmospheric Sao Paulo circuit, may not prove to be straightforward.

The local government has said it intends to privatise the facility as part of plans to reduce public expenditures for the city.

Sao Paulo mayor Bruno Covas attended Sunday's race and told reporters the city planned to push ahead with privatisation and secure the race's future.

A bill for that purpose needs to be approved in a second round vote in the local assembly, with no date set.

"The race is important for the city, we have all the interest to keep it," Covas said.

The final privatisation model, which has concerned some in Brazilian motor racing with a proposal for residential buildings on part of the site, is considered a key to the extension talks.

Some local drivers recently met Covas at City Hall to discuss the situation.

Interlagos is the only South American race on the calendar but Brazil no longer has any drivers competing in Formula One following the departure last year of 2008 overall runner-up Felipe Massa.

Sunday's sellout race was won by five-times champion Lewis Hamilton, clinching the constructors' title for Mercedes, after Red Bull's Max Verstappen was caught in a collision with Force India back-marker Esteban Ocon while leading.

That controversial incident proved a major talking point, with Verstappen angrily confronting Ocon afterwards and giving him several shoves.

Formula One, under the ownership of U.S.-based Liberty Media, has plans to expand the calendar and include new venues such as Vietnam as well as more races in the United States.

The sport's commercial managing director Sean Bratches said last week that Formula One wanted to keep its 'heritage races' but also had to be run as a business.

A Formula One spokesman said there was no rush to secure a contract extension for Brazil and there was still plenty of time.

"Brazil is an important country for F1," he added.