Horner: Mercedes still favourite for 2017 F1 titles

Mercedes won its third successive constructors' championship last season, while Nico Rosberg added the drivers' title to Lewis Hamilton's successes in 2014 and 2015.

This year will feature faster, more aggressive-looking cars with wider front and rear wings and bigger, wider Pirelli tyres in the most significant rules shake-up since 2009.

While Horner believes the overhaul provides Red Bull, who emerged as Mercedes' closest challenger in 2016, a chance to close the gap, he still thinks Mercedes will be the team to beat.

"It's going to be tough to overcome Mercedes," said Horner. "They go into the year as the clear favourites.

"They have won three consecutive world championships, they've won 50-odd grands prix in the last three years.

"We're just hopeful we can close that gap so we don't have predictable results every grand prix weekend.

"With the new regulations, it should balance out the emphasis between chassis and engine.

"We're confident we should make a bit of progress over the winter with the engine.

"The regulations are a clean sheet of paper for everybody so you don't know where you sit at the moment compared to your opposition.

"It's an opportunity or it's a challenge we're looking forward to but it's only really when we get to Melbourne that we'll get a glimpse of where the competitive ranking is."

With teams starting with new concepts for 2017, former Williams technical chief Pat Symonds is expecting aerodynamic development to be "relentless".

Horner believes it will be a development race with "easy gains" to be made early on.

"You hope that you haven't missed something like the double diffuser, where there is an interpretation of the regulations that someone has spotted that generates an advantage," he said.

"The regulations aren't quite as dramatic as they were from '08 to '09 but they still represent a great opportunity to make the cars significantly quicker.

"It's going to be a development race next year and there will be easy gains at the beginning of any development cycle.

"That relentless pursuit of chasing upgrades will be a key part of certainly next year."