GREATER NOIDA, India (AFP) - Germany's Nico Rosberg on Thursday insisted that Formula One was still interesting for the fans despite Sebastian Vettel's march towards a fourth straight title.

Vettel's runaway success has earned him jeers from supporters of rival teams, with Lewis Hamilton even suggesting it was sending TV viewers to sleep.

But Mercedes driver Rosberg said there was exciting racing behind Red Bull's Vettel, who will win the championship if he finishes in the top five in Sunday's Indian Grand Prix.

"Forget what's happening in front," Rosberg said at a promotional event in New Delhi late on Wednesday.

"Vettel may be out there in the front all alone, but aren't you seeing what's happening just behind him?

"Aren't the contests between drivers behind him interesting? The crowds are enjoying it, right?"

The only way Vettel can be denied is if he fails to win another point this year - provided Ferrari's Fernando Alonso wins at least three of the last four races and finishes second in the other.

But there are at least five drivers bunched together behind Alonso who are jostling for position in the final season's standings.

Alonso leads by 30 points over third-placed Kimi Raikkonen, who is himself only 16 points ahead of Hamilton and 29 points in front of Red Bull's Mark Webber.

Rosberg, winner of the Monaco and British grands prix this season, is currently lying sixth with 22 points separating him from Webber.

The race is also tight in the constructors' championship - behind Red Bull, who are also expected to snare the team title this weekend.

Second-placed Ferrari, who trail Red Bull by a whopping 148 points, are only 10 points ahead of Rosberg's Mercedes and 33 points in front of Lotus.