Secretary of State Rex Tillerson said on Monday that dictator Bashar al-Assad had killed “more of his own people” in the recent chemical attack in Syria and that he hopes Assad “will not be a part” of the future in that country.

Tillerson’s comment, presented as a statement at the start of a press conference in Italy, is the strongest indication yet that the Trump administration sees Assad’s departure as part of the solution to ending the Syrian Civil War. The more than six-year-old conflict has cost hundreds of thousands of lives, including women and children.

Aside from the Assad regime, the Syrian population also faces threats from radical Islamic terrorists, including the so-called Islamic State, or ISIS, and al-Qaeda.

“Last week, Bashar al-Assad’s regime killed even more of its own people using chemical weapons,” Tillerson said. “Our missile strike in response to his repeated use of banned weapons was necessary as a matter of U.S. national security interest.”

“We do not want the regime’s uncontrolled stockpile of chemical weapons to fall into the hands of ISIS or other terrorist groups who could, and want to, attack the United States or our allies,” Tillerson said.

“Many nations look to the Geneva process to resolve the Syrian conflict in a way that produces stability and gives Syria and the Syrian people the opportunity to determine their own political future,” Tillerson said. “And our hope is Bashar al-Assad will not be a part of that future.”

Ahead of his arrival in Moscow, Tillerson also placed the blame for the attack squarely on Russia.

“Russia has failed to uphold the agreements that had been entered into under multiple UN Security Council resolutions,” Tillerson said. “These agreements stipulated Russia as the guarantor of a Syria free of chemical weapons, that they would also locate, secure, and destroy all such armaments in Syria.”

“Stockpiles and continued use demonstrate that Russia has failed in its responsibility to deliver on this 2013 commitment,” Tillerson said. “It is unclear whether Russia failed to take this obligation seriously or Russia has been incompetent, but this distinction doesn’t much matter to the dead.”

“We can’t let this happen again,” Tillerson said.

In response to a reporter’s question, Tillerson repeated his belief that Assad’s days are numbered, but he said that what replaces the regime is also important.

“I think it is clear to all of us that the reign of the Assad family is coming to an end; but the question of how that ends and the transition itself could be very important, in our view, to the durability, the stability inside of a unified Syria, and its stability and durability of the outcome going forward,” Tillerson said.

Last week, Tillerson answered another reporter’s question about Assad and said his removal was already in the works.

“So will you and President Trump organize an international coalition to remove Assad?” the reporter asked.

“Those steps are under way,” Tillerson said.

And during the Q. and A. in Italy Tillerson made clear Russia has a choice to make.

“Russia can be a part of that future and play an important role, or Russia can maintain its alliance with this group, which we believe is not going to serve Russia’s interest longer-term,” Tillerson said. “But only Russia can answer that question.”

On Sunday, a Russian official said Russian President Vladimir Putin does not have plans to meet with Tillerson face-to-face, even though the two have met numerous times in the past when Tillerson was the CEO of ExxonMobile.

“We have not announced any such meetings and right now there is no meeting with Tillerson in the president’s diary,” spokesman Dmitry Peskov told reporters on a Monday press conference call, according to Reuters.

Also on Sunday, Tillerson laid a wreath in the Tuscan village of Sant’Anna di Stazzema, the site of a Nazi massacre of more than 500 civilians during World War II. He also referenced the chemical weapon attack in Syria and pledged to protect innocent people around the globe.

“We rededicate ourselves to holding to account any and all who commit crimes against the innocents anywhere in the world,” Tillerson said. “This place will serve as an inspiration to us all.”