“I’m a bit concerned about the outlines of the strategy as I understand it. I think it’s based on assumptions that, quite frankly, are not the right ones,” the Florida Republican said in an interview with ABC News.
The Syria strategy has come under spotlight after President Donald Trump ordered the US military to carry out a barrage of missile strikes against a Syrian airfield early on Friday.
Trump said the operation was in response to a suspected chemical attack, which Washington insisted was carried out by Syrian fighter jets operating from the base.
The Syrian government has strongly denied responsibility for the gas attack, and there is no evidence that it was behind the incident.
Rubio, a White House contender in the 2016 presidential election, said "there has to be a strategy outline based on reality."
The senator, however, said the US must remove Syrian President Bashar al-Assad from power before it can defeat Daesh in the country.
The comments were in reference to Secretary of State Rex Tillerson’s assertion that there was “no change” in US policy and that the focus was still the defeat of Daesh.
Foreign policy experts argued that the recent military action exposed the lack of any coherent policy on Syria by the Trump administration.
That has also been evident in conflicting statements by administration officials.
The US ambassador to the United Nations, Nikki Haley, said the ouster of President Assad was a priority for the White House.
“There’s not any sort of option where a political solution is going to happen with Assad at the head of the regime,” Haley said in an interview with CNN over the weekend.