MOSCOW (AP) — Russia’s top diplomat accused the United States on Wednesday of carrying out an unlawful attack against Syrian President Bashar Assad’s forces as he opened a fraught meeting with visiting U.S. Secretary of State Rex Tillerson.

Sergey Lavrov, Russia’s foreign minister, said Russia had lots of questions about the Trump administration’s “very ambiguous” and “contradictory” ideas. In an ominous start to their meeting, Lavrov said it was important for Moscow to understand the “real intentions” of the Trump administration.

“We have seen very alarming actions recently with an unlawful attack against Syria,” Lavrov said. “We consider it of utmost importance to prevent the risks of replay of similar action in the future.”

Tillerson, the first Trump Cabinet official to visit Russia, conceded the U.S. and Russia had “sharp differences” that have been obstructing cooperation between the two powers. He said he was seeking to “better understand” the differences so that they could be narrowed.

“We both have agreed our lines of communication shall always remain open,” Tillerson said.

The tense start to Tillerson’s visit illustrated the widening chasm between the former Cold War foes. Early expectations of an easy rapport between the Trump administration and Russia have crashed into reality as the two countries have traded escalating accusations over what happened last week in a chemical attack in Syria.

As their envoys gathered in Moscow, President Donald Trump and Russian President Vladimir Putin were voicing protests of their own.

“Frankly, Putin is backing a person that’s truly an evil person,” Trump told the Fox Business Network, referring to Assad. “I think it’s very bad for Russia. I think it’s very bad for mankind.”

Of Assad, Trump added: “This is an animal.”

And Putin, who U.S. intelligence agencies say tried to help Trump get elected, insisted that relations with the U.S. had only gone downhill since Trump took office in January.

“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.

It was unclear whether Putin, who once gave Tillerson an “Order of Friendship” award, would grant the visiting American an audience in Moscow. Though the Kremlin had declined to say whether the leaders would meet, Putin spokesman Dmitry Peskov said Wednesday: “There is a certain likelihood.”

Tillerson is on a thus-far-futile mission to persuade Russian President Vladimir Putin to abandon support for Syrian President Bashar Assad. The fallout from Assad’s chemical attack last week and the U.S. airstrikes that Trump ordered in response have plunged the United States and Russia into tensions rarely seen since the Cold War.

Before flying to Moscow, Tillerson issued an ultimatum to Putin: Either side with the U.S. and likeminded countries, or with Assad, Iran and the militant group Hezbollah. But Russia made clear it had no intention to acquiesce. Putin quickly invited the Syrian and Iranian foreign ministers to Moscow on Friday, the day after Tillerson departs.

“Our policy is consistent and it’s formulated exclusively on the basis of international law and not under the impact of current opportunistic motives or false choice: ‘You are with us or against us,'” Lavrov told Tillerson.

Adding further fuel to rising tensions: the White House’s move to circulate declassified U.S. intelligence accusing Moscow of aiding Assad’s government in covering up a gruesome, nerve gas attack that killed more than 80 people. The U.S. also accused Russia of mounting a disinformation campaign aimed at exonerating Assad from blame for the attack.

Russia has insisted it was Syrian rebels — Assad’s forces — that were responsible for the chemical weapons. Intelligence services from several Western countries dispute that claim. The health minister in Turkey, which treated many of the attack’s victims and conducted autopsies on others, said Tuesday that test results conducted on victims confirmed sarin gas was used.

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Associated Press writers Vladimir Isachenkov, Nataliya Vasilyeva and Jim Heintz contributed to this report.

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Reach Josh Lederman on Twitter at http://twitter.com/joshledermanAP