Red Bull are willing to give Daniel Ricciardo time to decide his future, acknowledging that his next move will be a "very important one" given his age.
Ricciardo has been with the Red Bull family ever since he entered Formula 1.
It was Red Bull who organised his HRT debut before promoting him to Toro Rosso in 2012 and Red Bull Racing in 2014.
The Aussie, though, has been linked to a move away from the team come 2019 with the rumour mill suggesting either Ferrari or Mercedes could be his next destination.
— Daniel Ricciardo (@danielricciardo) November 1, 2017
And while Red Bull would like an answer sooner rather than later, Horner says they will give the driver time to decide – even if it takes "another six months."
"The next move he makes at 28 years of age is a very important one for him," the Red Bull team boss told Reuters.
"So of course I'm sure he's going to take the time to make sure the decision is right for him.
"But he knows the intent very clearly, and I've discussed it with him, is that we want him in the team.
"If that takes another six months, then so be it."
He added: "He knows how we go about our racing and how we treat the two drivers, which he's extremely comfortable and happy with.
"I think, as his character has developed and as his personality has come across, he sees the fit between Daniel Ricciardo and Red Bull.
"I think he sees the capability that we have within the team. And I think he's very happy in the team."
Experience the full coverage of the FIA Formula One season throughout 2017 on FOX Sports Play, where you can watch LIVE races from angles unlike any other, highlights, interviews, behind the scenes and many more. Don’t miss it!