Christian Horner admits Red Bull Racing could be forced to skip the first Formula 1 test of the 2016 pre-season unless it can secure an engine deal imminently.

Red Bull remains without an engine for the 2016 season after its bitter divorce from Renault and subsequent rejections of supply from Mercedes and Ferrari, while a mooted deal with Honda is being blocked by McLaren.

Though it remains possible that Red Bull could quit the sport if it can't secure a competitive engine, even if the FIA and FOM do succeed in their attempts to force a deal through, Horner believes time is running out to get the car ready for the first test of 2016 in February.

"At the moment we're right on the limit to be at the first test. The team at Milton Keynes have demonstrated their abilities to work to massively tight deadlines and I'm sure we'd be able to meet whatever targets we need to, as we come to a decision in the next couple of weeks.

"We're working hard to find a solution and behind the scenes there is an awful lot going on to help us try and achieve that. Obviously there are certain obstacles in our way

Meanwhile, though Red Bull has been criticised for ending its Renault deal before confirming another one in its place, Horner suggests there are still no regrets.

"I think that frustration is, you have to understand all the history, the background and the circumstances and so it's always to look with hindsight and say this and say that but you know, there were things said from both sides. A lot of focus is placed on what Red Bull said but it's not a one-way street."