Rivals are forcing Red Bull out of Formula 1, says Adrian Newey

The clock is ticking on Red Bull's time in F1 as the four-time champion team remains without a power unit from 2016 onwards.

Red Bull decided last month it would end its relationship with supplier Renault a year ahead of the expiry of the contract, although the French manufacturer has yet to officially confirm a parting of the ways and was cool over the prospect of the deal being salvaged.

Mercedes has ruled out stepping into the breach as a replacement, while Ferrari is understood to have also declined, although again there has been no public proclamation.

Newey, Red Bull's chief technical officer and the most decorated designer in F1 history, believes the writing is on the wall for the Milton Keynes-based team.

"We're possibly going to be forced out of Formula 1 - Mercedes and Ferrari have refused to supply us out of fear," said Newey, speaking to Reuters.

"Unfortunately, our relationship with Renault is pretty terminal. There's been too much of a marriage breakdown, so we have no engine.

"Red Bull should not be put in a position where they're only there to make up the numbers."

The designer also believes the FIA should have done more to prevent F1 becoming so reliant on engine performance.

"Within the regulations, the engines can be balanced somewhat so that there's less of a performance disparity then there is at the moment, but the FIA has been unwilling to do this," he said.

"We need to get back to the position where all teams have access to an engine which is there or thereabouts - if it's a couple of per cent behind then OK, but when it's 10 per cent behind it's too big a gap.

"As an engineer, I'd liked to see more flexibility in the chassis regulations so that teams can find benefit through ingenuity and creativity."

Red Bull owner Dietrich Mateschitz has suggested an answer on whether the team remains in F1 will be due by the end of October.

Sister team Toro Rosso is closing in on a deal with Ferrari for the supply of a 2015-spec engine, although there remain numerous hurdles to clear yet for that scenario to come to fruition.