Republican Sen. John McCain of Arizona. Screenshot/CNN Republican Sen. John McCain tore into Secretary of State Rex Tillerson on Tuesday morning, telling CNN that Tillerson's recent comments about the US's policy in Syria represented "another disgraceful chapter in American history."

Tillerson told reporters while he was in Turkey last week that the "longer-term status of President [Bashar] Assad will be decided by the Syrian people."

The remark signaled a shift in the US's official position toward the Syrian strongman. Though they were criticized for failing to act against Assad, President Barack Obama and former Secretary of State John Kerry had long called for Assad to step down in a monitored transition of power.

The US's ambassador to the UN, Nikki Haley, took an even stronger position than Tillerson, telling reporters that the administration's "priority is no longer to sit there and focus on getting Assad out."

Haley's comments stood in stark contrast to those of the previous UN ambassador, Samantha Power, who directly confronted Assad and his Russian and Iranian allies during a UN Security Council meeting in December with a fierce address.

"Three member states of the UN contributing to a noose around civilians. It should shame you. Instead, by all appearances, it is emboldening you," Power said at the time. "You are plotting your next assault. Are you truly incapable of shame?"

In a press conference four months later, Haley told reporters that the Trump administration thought Assad was "a hindrance." She added that she believed he was a war criminal.

"Are we going to sit there and focus on getting him out? No," she said. "You pick and choose your battles."

A senior administration official described Haley's comments as "a measure of just realism, accepting the facts on the ground," according to Reuters.

The apparent shift comes as dozens of people reportedly were killed in an attack on Tuesday when a hospital that was treating civilians injured in chemical attacks was bombed. Activists described the attack as among the worst in the country's six-year war.

Russian President Vladimir Putin, right, and Syrian President Bashar Assad in Moscow in October 2015. AP

Some experts said Tillerson's and Haley's comments would be music to the ears of Russian President Vladimir Putin, who intervened in the Syrian civil war on behalf of Assad in late September 2015.

McCain, a Republican foreign-policy hawk who has called for a US military intervention in Syria, said Tuesday that he was sure Russia "took note of what our secretary of state said just the other day."

"One of the more incredible statements I've ever heard," he told CNN.

When asked what he thought of US President Donald Trump's foreign-policy doctrine, McCain said, "I don't see any doctrine right now."

Sen. Lindsey Graham, who has similar foreign-policy views, said in a statement last week, "If the press reports are accurate and the Trump administration is no longer focusing on removing Assad, I fear it will be the biggest mistake since President Obama failed to act after drawing a red line against Assad's use of chemical weapons."

The Obama administration's failure to enforce the "red line" it drew for intervention in Syria against Assad in 2012 has become arguably the biggest stain on the former president's foreign-policy legacy. Kerry acknowledged in December that the failure to follow through on the threat to retaliate against Assad for his use of chemical weapons to kill 1,500 people in August 2013 damaged the US's reputation in the region.

Obama opted instead for a deal brokered by Russia to ship Assad's chemical weapons stockpile out of Syria and destroy them. The US hailed the deal as a success, but Assad has evidently retained some of the weapons he promised to destroy. Syrian activists have reported three chemical attacks in the last week alone, according to The Associated Press, including the attack on Tuesday.

Watch McCain's remarks: