Helmut Marko has refused to rule out a move to Honda power for Red Bull at the end of the 2018 Formula One season, saying "everything is open".
Honda have endured a difficult time since returning to the sport with McLaren in 2015, managing two ninth-place finishes either side of ending the season sixth in the constructors' standings in 2016.
McLaren have partnered with Renault for the 2018 campaign, as Honda enter a new arrangement with Toro Rosso - Red Bull's sister team, who are also overseen by Marko.
In an interview on the F1 website, Marko was asked whether a successful partnership between Toro Rosso and Honda could lead to a future deal between the Japanese engine supplier and Red Bull.
"We are very happy with the Toro Rosso and Honda cooperation," he said. "Toro Rosso will put all its efforts into making a competitive chassis.
"We do believe in Honda - otherwise we wouldn't have made that deal. I am very impressed with the facilities that they have - and their determination to win.
"It is just a matter of bringing everything together and we believe that this moment will arrive sooner than everybody is expecting.
"We will observe very closely - beyond 2018, everything is open!"
Red Bull could be left with no option but to switch to Honda power for 2019 should they not extend their deal with Renault.
Ferrari and Mercedes are understood to have little appetite to add to their current supply commitments, leaving Honda as the only other manufacturer on the grid.
|Johnson, Landry tied for Texas lead as Mullinax sets course record|
|Gattuso, Mirabelli apologise to Milan fans after ´embarrassing´ Benevento loss|
|Marquez to start fourth after being stripped of Austin pole|
|Iniesta to make decision on his future public ´this week´|
|United want to win everything next year, says Wembley hero Sanchez|
|Cardiff edge Forest to boost promotion push|
|Bartomeu confirms Iniesta has an ´offer´ amid Chinese Super League reports|
|Messi second player to score in five Copa finals|
|Khan makes up for lost time with 40-second Lo Greco knockout|
|Mourinho challenges Alexis after Wembley star turn|
|Vieira ready for Arsenal job, says Guardiola|
|FA Cup win would represent successful season - Conte|
|Guardiola: I want Manchester City to be a Premier League machine|
|Marquez crashes before taking controversial pole in Austin|
|Sevilla 0 Barcelona 5: Suarez and Messi lead crushing Copa final win|
|Defending champion Selby dumped out in first round|
|AC Milan 0 Benevento 1: Rossoneri suffer again as bottom side stave off relegation...for now|
|Ulster stay alive in dramatic fashion as Bellini sparkles for Zebre|
|Semi-final pain for frustrated Kane|
|London stay was crucial to FA Cup Wembley win - Mourinho|
|Pochettino: Spurs need four more years – with me or another|
|Kaepernick honoured with Amnesty International award|
|He has not delivered optimal performances - Stoger explains Schmelzer omission|
|Kvitova and Pliskova put Czechs in control|
|Modric open to Ibrahimovic union in MLS|
|Spurs can´t keep doing this – Alli|
|Bulls keep Rebels waiting for South Africa win, Sharks beat Stormers|
|Heynckes highlights importance of ´psychology´ before Real Madrid clash|
|United are about winning titles and playing finals, says happy Herrera|
|Pogba and United the comeback kings again|
|Destructive De Villiers demolishes Daredevils|
|Giroud thanks Wenger for making his ´dream come true´|
|Borussia Dortmund 4 Bayer Leverkusen 0: Reus and Sancho star as Stoger´s side go third|
|Manchester United 2 Tottenham 1: Sanchez and Herrera seal comeback to book FA Cup final spot|
|Zaha´s no diver, insists Hodgson|
|Quiros maintains one-shot lead in Rabat|
|Championship Review: Wolves win title, Sunderland relegated|
|Nishikori fights back to reach Monte Carlo final|
|´Nothing compared to that night´ - Masters victory left Allen feeling flat|
|Imperious Leinster ease into Champions Cup final|
|Wilson backs Wenger for international role|
|West Brom comeback branded ´useless´ by Klopp|
|Injured Kyrgios doubtful for French Open|
|Packers QB Aaron Rodgers ventures into ownership, buys stake in NBA´s Bucks|
|Lewandowski breaks Bundesliga record in Bayern Munich victory|
|Watford 0 Crystal Palace 0: Stalemate edges both sides closer to survival|
|Inter not inferior to Roma and Lazio, Spalletti insists|
|Pogba and Sanchez start for Manchester United at Wembley|
|Gayle fires Kings XI to the top of the table|
|Klopp applauds Ings´ performance|
|Hannover 0 Bayern Munich 3: Lewandowski breaks Bundesliga record|
|Livermore urges West Brom to ´keep fighting´ as relegation looms|
|Eagles give QB Nick Foles a pay rise after Super Bowl win|
|Klopp blames ´dry pitch´ and referee for West Brom draw|
|Cardiff Blues book Challenge Cup final berth|
|Salah finds the net again to equal Premier League scoring record|
|Nadal marches on towards 11th Monte Carlo crown|
|West Brom 2 Liverpool 2: Careless Reds drop points to offer Baggies slim survival hope|
|Roma will be eyeing revenge against Liverpool, warns Ancelotti|
|Bayern hand Bundesliga debut to Lars Lukas Mai|
|Costa should be back for Arsenal second leg, reveals Simeone|
|Wenger could coach Paris Saint-Germain, says Emery|
|Crusaders survive the storm, Chiefs inflict more misery on Reds|
|Wenger changed the face of English football - Dixon|
|Rodgers shrugs off Arsenal talk|
|Knights leave it late against Tigers, Cowboys end winless run|
|Austin track a disaster, says Rossi|
|Clash between top two ´more decisive´ for Napoli, Allegri claims|
|Chongqing sponsor ´positive´ over Iniesta deal|
|Valverde´s quiet crisis management leaves Barca ready to clean up|