Russian President Vladimir Putin will meet with Secretary of State Rex Tillerson after all during his stay in Moscow, a Russian television station has reported.

Putin's spokesman had said Monday that the foreign leader did not plan to see Rex Tillerson, the US secretary of state. Tillerson was to meet with Foreign Minister Sergey Lavrov, instead.

But there appeared to be a volte-face by the Kremlin as a station close to Putin said there would be a meeting.

State Department spokesman Mark Toner said Tuesday that if an invitation comes, Tillerson will 'of course' accept, but it up to the Kremlin to make that offer.

The meeting - if it actually happens - is likely to be extremely tense.

Tillerson hammered Russia on Tuesday, saying in a statement that Russia had 'failed in its responsibility' to locate and destroy Bashar al-Assad's entire stockpile of chemical weapons.

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Russian President Vladimir Putin will meet with Donald Trump's chief diplomat after all during his stay in Moscow, a Russian television station has reported

The Kremlin did not say why Putin was avoiding Tillerson - who arrived in Moscow late Tuesday evening - after meeting repeatedly with his predecessor, John Kerry, only that he was not on the president's schedule

Semper fi: A handout photo made available by the US Department of State shows US Secretary of State Rex Tillerson posing for a photo with members of the Marine Security Guard Detachment at the US Embassy in Moscow, Russia

Tillerson (L) and US Ambassador to Russia John Tefft shake hands at a welcome ceremony at Moscow's airport today. There was no official Russian presence

Putin's plans appeared to change on Tuesday despite Tillerson hammering him on Syria, with a pro-Kremlin station saying the two would meet. He touched down in Moscow after the G-7 meeting in Lucca, Italy

'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.

He told a reporter afterward during a media availability that the US believes that Russia could be persuaded to switch sides now that it knows Assad is an 'unreliable partner.'

'Russia has really aligned itself with the Assad regime, the Iranians, and Hizballah. Is that a...long-term alliance that serves Russia’s interest, or would Russia prefer to realign with the United States, with other Western countries and Middle East countries who are seeking to resolve the Syrian crisis?' Tillerson said.

The US and its allies may already be chipping away at Russia's resolve.

Putin has reportedly changed his mind about seeing Tillerson - a man he once gave a friendship award to - during his visit to Moscow.

RBC, a Russian business broadcasting station, said Tuesday that a Putin-Tillerson face-to-face would happen. It cited two sources connected to Russian's foreign ministry, according to the Moscow Times.

The White House declined to comment on the matter.

Mark Toner, the State Department's top spokesman, said Tuesday in response to a question about the possibility of a meeting, that no offer had been made.

'If there is an invitation for him to meet with Putin, of course, he’ll do so. I think that’s a decision for the Kremlin to make and to announce, and up till now we’ve not seen such an offer extended,' Toner said. 'Now, it could come. So as I said...he’s certainly willing to meet with President Putin to discuss all of these issues.'

Tillerson is expected to discuss the White House's goals of 'defeating ISIS, and...creating the political environment necessary for the Syrian people to have new leadership' with Russian officials during his visit.

To meet those ends, the US will need the help of Moscow.

The White House's top spokesman said Monday that Tillerson will make sure that Russia 'fully understands' the situation on the ground in Syria.

He'll further remind the Kremlin during his visit of the agreement it made with the international community to oversee the elimination of Assad's chemical stockpile.

Russia offered to destroy Syria's chemical weapons in 2013, attesting afterward that it did. It obviously failed to live up to that commitment, the US says.

The Assad ally claims that airstrikes on terrorists led to an inadvertent hit on a warehouse storing the toxins that poisoned and killed more than 80 people.

Experts say the explanation is unlikely. The US, UK and other nations have said it was Assad.

'Getting them back on the same page, first and foremost, would seem the logical step,' White House Press Secretary Sean Spicer said. 'But secondly, and I guess equally important is to make sure that the areas we can find a commitment to defeat ISIS is something that we share.'

Tillerson flew to Russia from Europe on Tuesday, where he attended meetings with the United States' allies in the fight against ISIS.

At his press availability earlier in the day in Lucca, Italy, Tillerson said said the US wants to 'relieve the suffering of the Syrian people' and 'create a future for Syria that is stable and secure.'

'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,' he said. 'But only Russia can answer that question.'

The White House later accused Putin of spreading false information about the chemical weapons attack.

Putin claimed the Assad regime is being framed for the gas attacks and he has intelligence that 'some kind of substance' will be used in Damascus again.

'We have information that a similar provocation is being prepared ... in other parts of Syria including in the southern Damascus suburbs where they are planning to again plant some substance and accuse the Syrian authorities of using it,' Putin said after he was asked about further American missile strikes.

Senior White House officials said Tuesday they are 'very confident' that the attack was not committed by non-state actors, however.

'I think it's clear that the Russians are trying to cover up what happened,' one said.

Another White House official at the briefing suggested that Russia was complicit in the sarin gas assault because its troops are embedded with Syria's.

The official would not charge Russia with active involvement in the attack yet noted that the two countries' militaries have been operating 'closely' together for the better part of two years and have a relationship that goes back more than a decade.

'We do think that it is a question worth asking the Russians about how is it possible that their forces were co-locate with the Syrian forces that planned, prepared and carried out the chemical weapons attack at the same installation and did not have fore knowledge,' the official said.

Tillerson poses for a photo with members of the Italian Air Force before departing Italy en route to Moscow, Russia, at Pisa Military Airport in Italy

The White House held the briefing on Russia's claims about what happened in Syria ahead of Tillerson's meetings tomorrow with the Kremlin.

'This is an opportunity for the Russians to choose to stop the disinformation campaign,' an official said of Tillerson's trip.

Putin has continued to deny that Assad's regime was behind last week's attack in Idlib which killed 87 and says it will be calling on the United Nations to investigate.

At a news conference on Tuesday he likened last week's use of chemical weapons to the supposed existence of weapons of mass destruction that led to the invasion of Iraq in 2003.

'This ended with the country's destruction, with the growth of the terrorist threat and the appearance of the Islamic State on the international stage, no more, no less.'

Putin confirmed that Russia will urgently ask the global chemical weapons watchdog - the Organisation for the Prohibition of Chemical Weapons - to investigate Idlib.

White House officials said Tuesday afternoon that they'd welcome an OPCW review.

US officials expressed a 'very high degree of confidence' that Assad was responsible for the chemical weapons attack that Russia had previously claimed was an accident.

At the Pentagon today, Defense Secretary James Mattis said he had personally reviewed the intelligence 'and there is no doubt the Syrian regime is responsible for the decision to attack and the attack itself'

The chemicals spread after Syrian forces struck a terrorist warehouse filled with toxins, Putin's government had previously said.

'We think that the information is inconsistent with that narrative,' an official said. 'We don't see a building, again, with that chemical residue that we would expect if that Russian narrative was true.'

Spicer said Assad's actions are worse than Adolf Hitler's. Even the 1940s Nazi dictator 'didn't even sink to ... using chemical weapons,' he said.

One shocked reporter reminded Spicer that Hitler used poison gas to exterminate millions of Jews. Another gamely gave him a chance to sputter through a clarification.

The embarrassing gaffe came as about six million American Jews – and millions more around the world – celebrate Passover.

Hitler primarily used Zyklon B, a powerful cyanide gas, to exterminate Jews, gypsies, homosexuals, priests, political dissidents and other enemies of the state.

Describing that historical horror, Spicer declared that Hitler 'was not using the gas on his own people.'

HE GASSED THE JEWS! White House Press Secretary Sean Spicer said Tuesday that Assad's actions are worse than Adolf Hitler's. Even the 1940s Nazi dictator 'didn't even sink to ... using chemical weapons,' he said. One shocked reporter reminded Spicer that Hitler used poison gas to exterminate millions of Jews

At the Pentagon today, Defense Secretary James Mattis said he had personally reviewed the intelligence 'and there is no doubt the Syrian regime is responsible for the decision to attack and the attack itself.'

Asked about Russian complicity in the deadly chemical attack, Mattis said the intelligence only supports the current conclusion that the Syrian government is to blame.

'And beyond that we cannot say right now,' the general noted. 'We don't know anything beyond that.'

Mattis also pledged that the U.S. would not go to war with Russia over Syria.

'It will not spiral out of control,' Mattis said. 'As you know, Secretary Tillerson is in Moscow. We maintain communications with the Russian military and with the diplomatic channels. It will not spiral out of control.'

Mattis explained that keeping peace with the U.S. is in the Kremlin's interest.

'I'm confident the Russians will act in their own best interest and there's nothing in their own best interest to say they want this situation to go out of control,' he asserted.