Jahanbakhsh joined the Premier League side last summer from AZ Alkmaar where he finished the 2017-18 season as the leading scorer in the top Dutch division.
But a hamstring injury has limited the 25-year-old's impact for the English team and raised questions over his involvement in the Asian Cup which Iran last won in 1976.
Carlos Queiroz said Jahanbakhsh will be given every opportunity to prove his fitness, even though he may not be ready for the opening game against Yemen in Abu Dhabi on Jan. 7.
"From a medical and technical point of view, we have a strong belief that he will be able to recover for the competition, although possibly not for the first stage," the Portuguese coach told Reuters.
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Jahanbakhsh has been included in Iran's 23-man squad for the tournament but regulations allow coaches to replace players up to 24 hours before their first game on medical grounds if required.
Queiroz's team are among the favourites to win despite injuries which have ruled out midfielders Saeid Ezatolahi and Ali Golizadeh and defender Sadegh Moharrami.
Iran impressed during the World Cup in the summer against Morocco, Spain and Portugal and Queiroz believes his team have been unfortunate not to carry that form into the Asian Cup.
"After the World Cup we were living a good moment with our performances and the opportunities that most of our players got to live and play in good teams in Europe, but unfortunately we have been hit by a wave of injuries since September," he said.
"But we have a settled group with good foundations and good knowledge between all of them and we just need to turn these difficulties into belief and hope. We're going to try."
(Reporting by Michael Church; Editing by Robin Pomeroy)
