Rex Tillerson is due to meet with his Russian counterpart Sergey Lavrov in Moscow today
Donald Trump has ruled out using US troops in Syria as his Secretary of State prepares for talks in Moscow.
In an interview with Fox Business, the US president said he had no intention to "get involved" with the regime of Bashar al Assad.
He also explained what motivated him to carry out a cruise missile attack on a Syrian airbase.
He told the network: "We're not going into Syria. But... what I did should have been done by the Obama administration a long time before I did it.
"When I looked at the pictures on any show or any newspaper, but especially when you see them on television... and you see these beautiful kids that are dead in their fathers' arms, or you see kids gasping for life.
"And you know... it's over for them. They're hosing them down, hundreds of them. When you see that, I immediately called General Mattis. I said, what can we do?"
His comments came amid a row over what retaliation the US should take if chemical weapons are used again.
Vladimir Putin claimed fake chemical weapons attacks in Damascus were being planned as a possible justification for further US airstrikes in Syria.
The Russian president said Moscow had intelligence that "provocations" would be carried out with the sole purpose of pinning the blame on the Assad regime.
He told a TV news conference: "We have information from various sources that such provocations - I cannot call them otherwise - are being prepared in other regions of Syria, including in the southern outskirts of Damascus, where they are again planning to throw some kind of substance and accuse Syrian official authorities of using it."
He appealed to the United Nations to launch an official investigation into the attack, comparing allegations targeting Mr Assad to US claims that Iraq had weapons of mass destruction before invading the country in 2003.
Meanwhile, a White House official accused Moscow of orchestrating a campaign of misinformation to deflect blame away from the Assad regime and "confuse the world."
Moscow has rejected suggestions the Syrian government was behind the gas attack in Idlib province which killed more than 80 people, including many children, as has the Assad regime.
Mr Trump added that he was inspired by the need to do something but said the US would not be getting involved with forces loyal to Mr Assad.
He said: "We're not going into Syria. But when I see people using horrible, horrible chemical weapons, which they agreed not to use under the Obama administration, but they violated it."
Mr Trump's Secretary of State Rex Tillerson is due to meet with his opposite number Sergey Lavrov today and is expected to deliver a unified message from world leaders denouncing Russia's support for Assad.
The UK has joined with France and the US in a bid to get the UN Security council to investigate the chemical attacks.
Earlier on Tuesday, G7 foreign ministers rejected British Foreign Secretary Boris Johnson's calls to broaden sanctions against Russia and Syria, but they did reach agreement on a set of ambitions.
His attempts at taking action against any of Mr Assad's supporters appeared to be limited by the G7's other European members.