As their envoys gathered in Moscow, President Donald Trump and Russian President Vladimir Putin were voicing protests of their own.
Tillerson has a meeting set later Wednesday in Moscow with Foreign Minister Sergey Lavrov.
But on Monday, U.S. Secretary of State Rex Tillerson visited the site of a World War Two Nazi massacre in Italy and said Washington would never let such abuses go unchallenged.
U.S. Secretary of State Rex Tillerson says Russian Federation must choose between aligning itself with the U.S. and likeminded countries or embracing Syrian President Bashar Assad, Iran and the militant group Hezbollah.
The high-stakes talks between Tillerson and Lavrov come less than a week after the USA launched the airstrikes, triggering a deterioration in ties between the two governments.
Indeed, in a politically divided country, the seemingly only thing that unites Matteo Renzi's center-left Democratic Party, Silvio Berlusconi's center-right Forza Italia, the anti-establishment 5Stars and the far-right Northern League is that the parties all oppose the European Union sanctions on Russian Federation, advocating instead a softer line on Moscow. He told Fox Business Network that Mr Putin's support for Mr Assad is "very bad for Russia". Trump says it's also "very bad for mankind".
The missile attack has increased expectations that Trump is ready to adopt a tougher stance with respect to Russian Federation, and that he is ready to engage in world affairs instead of following the more isolationist stance he had previously taken.
Former Rams, Saints LB James Laurinaitis announces retirement
He was a second-round pick of the Rams in 2009, played there through 2015, and then played a year ago in New Orleans. He only appeared in five games during the regular season, due to being benched and then later being placed on IR.
Mr Tillerson said he wanted to understand why US-Russia differences exist.
"The level of trust at the working level, especially at the military level, has not become better but most likely has degraded", Putin said in an interview broadcast Wednesday by state television channel Mir. Washington and Moscow are trading sharp accusations about a chemical weapons attack last week in Syria.
It was unclear whether Putin, who once gave Tillerson an "Order of Friendship" award, would grant the visiting American an audience in Moscow.
Tillerson is traveling Tuesday to Moscow.
"Our policy is consistent and it's formulated exclusively on the basis of worldwide law and not under the impact of current opportunistic motives or false choice: 'You are with us or against us, '" Lavrov told Tillerson.
Putin also said Russian Federation has received intelligence about planned "provocations" using chemical weapons that would put the blame on the Syrian government. The White House has accused Russian Federation of trying to "cover up" Assad's role in the attack. Intelligence services from several Western countries dispute that claim.
Comments