(CNN) The US ambassador to the United Nations, Nikki Haley, has told CNN that removing Syrian President Bashar al-Assad from power is a priority, cementing an extraordinary U-turn in the Trump administration's stance on the embattled leader.

Two days after the US launched military strikes on a Syrian airbase in response to a chemical weapons attack widely blamed on the Assad regime, Haley said Assad's departure was inevitable.

But before Tuesday's chemical attack on the rebel-held town of Khan Sheikhoun, which killed 89 people, Haley had said toppling Assad was not a priority. President Donald Trump, before his election, described fighting ISIS and seeking Assad's removal at the same time as "idiocy."

After seeing images of the horrific aftermath of the chemical attack, Trump ordered a bombardment of the Shayrat airbase in western Syria, which the US believes was the launchpad for the strike. It was the first time that the US had struck the Syrian regime since the start of the six-year civil war

"Getting Assad out is not the only priority. So what we're trying to do is obviously defeat ISIS. Secondly, we don't see a peaceful Syria with Assad in there. Thirdly, get the Iranian influence out. And then finally move towards a political solution, because at the end of the day this is a complicated situation, there are no easy answers and a political solution is going to have to happen," she said in the interview with anchor Jake Tapper.

Photos: US launches strike against Syrian base In this image provided by the US Navy, the USS Porter fires a Tomahawk cruise missile from the Mediterranean Sea on Friday, April 7. On the orders of President Donald Trump, US warships launched between 59 Tomahawk missiles at a Syrian government airfield. US officials said the Shayrat airfield was home to warplanes that carried out a chemical attack against civilians earlier in the week. Hide Caption 1 of 13 Photos: US launches strike against Syrian base The USS Ross fires a missile from the Mediterranean Sea. All of these warship photos were provided by the US Navy. Hide Caption 2 of 13 Photos: US launches strike against Syrian base A Tomahawk missile is fired by the USS Porter. When announcing the attacks, Trump said it is vital to the "national security of the United States to prevent and deter the spread and use of deadly chemical weapons." Hide Caption 3 of 13 Photos: US launches strike against Syrian base Another view of a missile being launched from the USS Ross. Hide Caption 4 of 13 Photos: US launches strike against Syrian base The strikes are the first direct military action the United States has taken against the leadership of Syrian President Bashar al-Assad during the country's six-year civil war. Hide Caption 5 of 13 Photos: US launches strike against Syrian base "There can be no dispute that Syria used banned chemical weapons, violated its obligations under the Chemical Weapons Convention and ignored the urging of the UN Security Council," Trump said. "Years of previous attempts at changing Assad's behavior have all failed and failed very dramatically." Hide Caption 6 of 13 Photos: US launches strike against Syrian base Thirty-six of the Tomahawks were fired from the USS Ross and the other 23 were launched from the USS Porter, a US defense official told CNN. Hide Caption 7 of 13 Photos: US launches strike against Syrian base Damage is seen in the area of the Shayrat airfield, near the Syrian city of Homs, on Friday, April 7. The Pentagon said the strike, which began at 8:40 p.m. ET Thursday (3:40 a.m. local time Friday), targeted aircraft, storage facilities and other logistical materials. Hide Caption 8 of 13 Photos: US launches strike against Syrian base People inspect debris near the Shayrat airfield. Syrian President Bashar al-Assad said the United States had carried out an "unjust and unabashed assault" against Syria which "shows nothing but short-sightedness, a narrowness of vision and a blindness to political and military realities." Hide Caption 9 of 13 Photos: US launches strike against Syrian base A plane is visible under an arch at the Shayrat airfield. Hide Caption 10 of 13 Photos: US launches strike against Syrian base The ground is blackened at the Shayrat airfield. A statement from Syria's general military command said the strikes caused "extensive material damage" and undermined counterterror operations by the Syrian army. Hide Caption 11 of 13 Photos: US launches strike against Syrian base Syrian jets remain parked at Shayrat. An initial damage assessment was that 58 of the 59 US missiles "severely degraded or destroyed" their intended targets, according to a US defense official. Hide Caption 12 of 13 Photos: US launches strike against Syrian base This satellite image, released by the US Department of Defense, is a damage assessment photo of the Shayrat airfield. Hide Caption 13 of 13

Haley said that the Trump administration's view was that a political solution would not happen with Assad in power, though she stopped short of saying Assad's departure was now official US policy.

"If you look at his actions, if you look at the situation, it's going to be hard to see a government that's peaceful and stable with Assad," she said.

"Regime change is something that we think is going to happen because all of the parties are going to see that Assad is not the leader that needs to be taking place for Syria."

US Secretary of State Rex Tillerson was more equivocal about Assad's future on Sunday. He told CBS's "Face the Nation" that the threat of ISIS would first need to be reduced, then "I think we can turn our attention directly to stabilizing the situation in Syria."

Change of tone

The decision to carry out strikes against the regime and the change in tone from Haley follows Trump's comments that the chemical attack "crossed a lot of lines for me."

Five days before the Khan Sheikhoun attack, Haley had indicated the US had ditched the Obama administration's policy of removing Assad.

"Our priority is no longer to sit and focus on getting Assad out," Haley had told reporters on March 30. On the same day, Tillerson said on a trip to Turkey that the "longer-term status of Assad would be decided by the Syrian people."

Russia has claimed Tuesday's deaths in Khan Sheikhoun were caused by a Syrian regime airstrike on a rebel-controlled chemical weapons facility.

Syria has given a murky account of what happened, but denies deliberately carrying out a chemical attack and blames "terrorist groups" for the deaths.

Lavrov said he supported a "thorough and impartial" investigation.

Russia-US tensions rise

Haley on Friday warned that the United States was prepared to take further action in Syria, but the Trump administration has refused to be drawn on what those next steps would be.

Tensions between Russia and the US have increased sharply since Trump ordered the missile strikes, and Russia has sent a frigate armed with cruise missiles to a port in western Syria in an apparent show of force in response to the US action.

The Russian frigate, the Admiral Grigorovich. The ship, which is armed with cruise missiles, was reportedly entering the Mediterranean en route to a logistics site in Syria, Russian state media said.

Russia is Syria's most powerful ally and has propped up the Assad regime with air power.

The US has said the Pentagon is looking for any evidence the Russian government knew about or was complicit in the chemical attack.

A US military official told CNN the Pentagon was examining specifically whether a Russian warplane had bombed a hospital in Khan Sheikhoun five hours after the initial chemical attack, with the aim of destroying evidence. Russia flatly denies the allegations.

On Sunday, Syrian state media cited a statement by a group calling itself the "Joint Operations Command Center of Russia, Iran and allied forces" saying that the US strike on Syria had "crossed red lines" and that it would "respond strongly to any aggression on Syria."

But the group does not appear to be linked to the Russian or Iranian governments, and Russian and Iranian officials have not used the same language.

In her interview with CNN, Haley came down hard on Russia, reminding viewers that Moscow had said it would ensure chemical weapons would not be used in Syria.

"Either they knew that there were chemical weapons and they knew there was going to be chemical weapon use, and they just hid it from the international community, or they are being played for fools by Assad -- by him having chemical weapons and they're just in the dark and they don't know anything about it," she said.

Haley added that US intelligence showed there was no doubt the Syrian regime was behind the chemical attack.

JUST WATCHED Syrian survivors detail moment of attack Replay More Videos ... MUST WATCH Syrian survivors detail moment of attack 02:28

"I think the international community has pretty much spoken and Russia is out there on an island saying that Assad didn't do it, because everybody else is very clear and knows that Assad did," she said.

Tillerson and his Russian counterpart, Sergey Lavrov, spoke by phone on Saturday, according to the Russian Foreign Ministry, which said the US had initiated the call.

"Lavrov stressed that an attack on a country whose government is fighting terrorism only plays into the hands of extremists creates additional threats to regional and global security," the statement said. Lavrov said US allegations that Syria carried out the chemical attack "do not correspond to reality."

The two ministers are scheduled to meet in Moscow on Wednesday for talks.

The US strike

US officials said the strike against the Shayrat airbase hit aircraft, fuel storage, weapons dumps and other equipment, and was aimed at sending a message to the Syrian regime that the use of chemical weapons would not be tolerated.

But new airstrikes on Saturday, believed carried out by the Syrian regime or Russia, targeted Khan Sheikhoun again, raising criticism that the US action had been ineffective and should have aimed to destroy the facility's runway.

The reason you don't generally hit runways is that they are easy and inexpensive to quickly fix (fill in and top)! — Donald J. Trump (@realDonaldTrump) April 8, 2017

Trump tweeted in defense on Saturday night that targeting a runway made little sense and they were easily repaired.