NSW police assistant commissioner Michael Fuller was the first high-ranking officer in command at the siege at Sydney's Martin Place on December 15, 2014.
He is being questioned about the police response to the incident which left gunman Man Haron Monis and hostages Tori Johnson and Katrina Dawson dead.
He told officers to "contain and negotiate" with Monis, saying not enough was known to order a forceful response even after a warning shot had been fired.
"My fear was any action, deliberate action, would certainly have caused a loss of life and I'm not talking about the perpetrator," Mr Fuller told the inquest on Wednesday.
A report by UK counter terrorism experts has said police should have immediately entered the building after Monis first fired his shotgun at 2.03am.
Ten minutes and 37 seconds later, Monis forced Mr Johnson to his knees and executed him with a point-blank shot to the head.
Mr Fuller disagrees with the UK report, saying community expectations in that country were different and led to different police responses.
"Strong action by police after a warning shot would likely cause someone's death," he said.
Balancing the attempt to preserve life and negotiate with the perpetrator against the possibility of taking action to end a violent stand-off was difficult and seems much easier in hindsight, the court heard.
"That will forever be the challenge of responding to these situations," Mr Fuller said.
"You would be trying to piece together a very difficult puzzle to make a very difficult decision."
Mr Fuller was in command at the scene from 9.50am until about 12.10pm but was asked about the actions of those in command more than 12 hours later as the siege escalated to its bloody conclusion.
"I don't think there were enough pieces of the puzzle to justify us going in," he said.
"Based on all the information coming in we didn't have the power to go in."
The inquest on Tuesday heard more about the "contain and negotiate" strategy.
Describing the early moments of the siege, Mr Fuller said police were uncertain about how many captives were inside and would not have stormed the building unless Monis had started shooting.
"There was no information to suggest there is any immediate threat in that environment to any of the hostages," he said.
"There was an enormous amount we needed to know."
The inquest continues.
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