Suggesting that there can be no peace in Syria while Assad remains in power, the United States stepped up pressure on Monday on Russia to rein in Syrian President Basharal-Assad, warning that any further chemical attacks would be "very damaging" to their relationship.
President Donald Trump's top advisers took to today television talk shows to set the stage for a diplomatic confrontation in Moscow this week when US Secretary of State Rex Tillerson meets with Russian Foreign Minister Sergei Lavrov.
It will be their first face-to-face encounter since US cruise missiles slammed into a Syrian air base early Friday Damascus time in retaliation for a suspected sarin gas attack on April 4 that killed at least 87 civilians in Syria's northern Idlib province.
Tillerson said the chemical attack had been preceded by two others in March.
US officials said the presence of Russian advisers at the airfield used to launch the attack raised questions about how they could not have known.
Tillerson stopped short of accusing the Russians of complicity. "But clearly they've been incompetent and perhaps they've just simply been out maneuvered by the Syrians", he said on ABC's "This Week."
If Syria carries out any further chemical attacks, "that is going to be clearly very damaging to US-Russian relations", Tillerson warned.
"I do not believe that the Russians want to have worsening relationships with the US, but it's going to take a lot of discussion and a lot of dialogue to better understand what is the relationship that Russia wishes to have with the US."
He said he would call on Russia "to fulfill the obligation it made to the international community when it agreed to be the guarantor of the elimination of the chemical weapons, and why Russia has not been able to achieve that is unclear to me."
Moscow has sought to deflect blame from its long-time ally Assad over the incident and says Syrian jets struck a rebelarms depot where "toxic substances" were being put inside bombs.
The US retaliatory strike marked the first time the United States has intervened directly in the Syrian civil war against Assad's Russian- and Iranian-backed regime, raising questions about Washington's next steps.
"The entire administration was in agreement that this was something that had to be done", Nikki Haley, the US ambassador to the United Nations, said on NBC's "Meet the Press."
"This was something that needed to tell Assad, 'Enough is enough'. And this is something to let Russia know, 'You know what? We're not going to have you cover for this regime anymore."