By Alan Baldwin
(Reuters) - Four-times world champion Sebastian Vettel will appear before Bahrain Grand Prix stewards on Sunday for allegedly failing to respect warning flags in qualifying for his first race with Aston Martin.
The summons for not respecting double-yellow flags at turn one capped a frustrating day for the German, who had hoped for a strong showing after leaving Ferrari, but instead qualified 18th of the 20 drivers.
He had been earlier cleared, along with others, of ignoring single yellow flags waved at turn eight.
Vettel had to slow when Russian rookie Nikita Mazepin spun his Haas, which meant the Aston Martin driver was unable to set a faster lap and reach the second phase of qualifying as expected.
The man who won his titles with Red Bull between 2010-13 had already endured a difficult start to the season with the fewest laps of anyone in testing.
"Certainly I think there was the potential to be a lot faster," he told Sky Sports television.
"We just made it across the flag (to start a final flying lap) and then I had the issue with the yellow flags during the lap, so that made it a little bit impossible to come back, but it's what it is.
"We would have hoped for a better start ... for sure I'm upset and angry, it wasn't our fault in a way not to make it through, but you have to take it."
Vettel's Canadian team mate Lance Stroll qualified 10th.
(Reporting by Alan Baldwin, editing by Toby Davis)