Secretary of State Rex Tillerson held an unexpected meeting Wednesday with Russian President Vladimir Putin, a Kremlin spokesperson confirmed.

The unscheduled talk came amid warnings from Moscow that the U.S. missile strike on a Syrian airbase in response to an alleged chemical weapons attack must not be repeated.

The Russian authorities earlier said a meeting with Putin was not on the agenda, but Kremlin spokesman Dmitry Peskov told reporters the Russian leader could meet with Tillerson “if it is decided” that he needs to be briefed on the outcome of the the secretary's talks with his Russian counterpart, Sergey Lavrov.

The confirmation of the face-to-face encounter came as the meeting was underway.

Tillerson, the first Trump administration official to visit Russia, also met with Lavrov in Moscow to urge the Kremlin to end its support for Syrian President Bashar Assad, a close Russian ally who has depended on Russian military support in a six-year-old civil war.

President Trump ordered the strike on a Syrian air base last week, citing a chemical attack that killed at least 86 people that he blamed on the Assad government.

In an interview broadcast Wednesday before the meeting with Tillerson, Putin said relations with the U.S. have worsened in the first few months of Trump’s presidency.

“It can be said that the level of trust at the working level, especially at the military level, has not become better but most likely has degraded,” he told state broadcaster Mir TV.

Putin also charged that the U.S. broke international law by striking the air base without providing evidence that the Syrian government used chemical weapons.

It was not the first meeting between the two men. Tillerson, as CEO of Exxon, had a close relationship with the Russian leader forged over business dealings in the past. In 2013, Putin personally awarded Tillerson the Russian Order of Friendship while the two met to negotiate ExxonMobil's $50 billion deal for Russian oil and gas rights.

On Tuesday, top U.S. officials rebuked Russia for either being complicit in the April 4 chemical attack or incompetence for failing to ensure that Assad destroyed all of his chemical weapons in 2013, as Russia promised it would guarantee.

Defense Secretary James Mattis said military intelligence confirmed that the Syrians dropped a lethal nerve gas on a rebel-held town and rejected Russian claims that the chemical was released when Syrian aircraft bombed a rebel lab.

The White House also said there is overwhelming evidence that Syria used a sarin nerve agent and that Russia is trying to help Assad's government cover up the illegal use of chemical weapons.

Kremlin spokesman Dmitry Peskov said that calls for Russia to distance itself from Assad are "short-sighted" and "absurd," because they disregard the need to fight terrorism and to find a political solution to the crisis in Syria.

"Most recently, we saw rather alarming steps, when an unlawful attack against Syria was carried out," Lavrov said at the meeting with Tillerson, according to Russian news agency TASS.

"Russia’s leadership has already voiced its principal assessments in this respect. We believe it is of principal importance to prevent risks of a repeat of such steps in the future," he added.

Tillerson said the U.S. and Russia had “sharp differences” that he was seeking to “better understand” so they can be narrowed.

“We both have agreed our lines of communication shall always remain open,” he said, according to the Associated Press.

Putin has said that Russia will appeal to the United Nations to investigate the chemical attack.

On Tuesday at a G7 summit in Italy, Tillerson said Russia must choose between aligning itself with the U.S. and other Western nations or Assad, Iran and the militant group Hezbollah.

President Trump told Fox Business Network’s Mornings with Maria that Putin is "backing a person that's truly an evil person" in his support for Assad. The interview was scheduled to air Wednesday morning.

Russia's foreign ministry said it hoped for constructive talks with Tillerson on the eve of the meetings.

"In the course of the forthcoming talks we would like to realize first and foremost to what extent the United States is aware of the need for stabilization and normalization of bilateral relations," the ministry said in a statement carried by TASS on Tuesday.

Russia is also hoping Tillerson's trip will help it better understand Washington’s plans for North Korea, TASS reported.