Donald Trump considered launching a strike three times as big on Syria, potentially including hitting Russian air defence systems, but was dissuaded by James Mattis, his defence secretary.
The Pentagon presented Mr Trump with three options for how to respond to the chemical attack by the Syrian regime in Douma on April 7, the Wall Street Journal reported.
A first, and most cautious, option consisted of a limited strike on Syrian chemical weapons facilities, while a second targeted those plus military command posts.
The third option had the aim of devastating Bashar al-Assad's military forces and could have targeted Syrian-based Russian air defence capabilities as part of that.
Such a strike would have been three times the size of the military action that was eventually launched by the US, UK and France in the early hours of Saturday.
Syria - The targets
In all, 105 missiles were launched at Syria.
During several days of intense planning meetings with his top national security advisers last week Mr Trump was said to have asked about hitting both Russian and Iranian targets if that was required to hurt Assad militarily, the Wall Street Journal reported.
He and Nikki Haley, the US ambassador to the United Nations, were said to have been pushing for a more robust strike.
But having laid out the three options Mr Mattis, according to the report, urged caution and suggested the third one could lead to an escalation by Russia or Iran.
The strike that ultimately happened reportedly drew from the first two options that he had presented.
That decision was being seen in Washington as confirmation of the elevated standing of Mr Mattis within the administration.
Asked whether Mr Trump had been pushing for proposals that included hitting Russian and Iranian targets in Syria, Sarah Sanders, the White House press secretary, said "a number of options" had been, and remained, on the table.
She said: "We're not going to get into any other options that were on the table.
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"We're going to continue to keep a number of options on the table if Syria and Russia and Iran don't show to be better actors in this process.
"So, I can't go any further than the targets that were part of the strike and successfully hit."
Meanwhile, Mr Trump dismissed claims by Syria and Russia that some US missiles were shot down.
He said: "We had well over 100 missiles. They didn't shoot one down. Their equipment didn't work too well...every one (of ours) hit its target, not one shot down."
John Bolton, Mr Trump's new national security adviser, was said to have pushed for the toughest response possible, but not to have advocated the third option, believing it could draw the US further into a conflict in Syria.
The three Syrian targets ultimately chosen were involved in the "research, development and deployment" of chemical weapons, the Pentagon said.
One was a scientific facility near Damascus and the other two were chemical weapons storage sites near Homs, one of which had been used as a military command post.
The strike involved more than double the number of missiles used in the US air strike on Syria in April 2017.