Barack Obama greets Donald Trump during January's inauguration ceremonies. (Carlos Barria/Reuters)

President Trump on Tuesday blamed his predecessor, Barack Obama, for Syrian President Bashar al-Assad's suspected use of chemical weapons in an attack that left dozens, including women and children, dead this week.

In a written statement, Trump called the attack “heinous” but blamed it on the Obama administration's failure to impose consequences on Assad for his past use of chemical weapons.

“Today’s chemical attack in Syria against innocent people, including women and children, is reprehensible and cannot be ignored by the civilized world,” Trump said Tuesday. “These heinous actions by the Bashar al-Assad regime are a consequence of the past administration’s weakness and irresolution.

“President Obama said in 2012 that he would establish a 'red line' against the use of chemical weapons and then did nothing,” he added. “The United States stands with our allies across the globe to condemn this intolerable attack.”

While the statement declared that the attack “cannot be ignored,” it offered no path forward.

Trump's brief comments also made no mention of Russia or Iran, both of which support the Assad regime. By contrast, a longer statement from Secretary of State Rex Tillerson singled out those country's roles in enabling the Assad regime.

Doctors and activists in rebel-held areas have blamed the Syrian government for a sharp increase in chemical attacks since the end of last year. (The Washington Post)

“While we continue to monitor the terrible situation, it is clear that this is how Bashar al-Assad operates: with brutal, unabashed barbarism,” Tillerson said in a written statement. “Those who defend and support him, including Russia and Iran, should have no illusions about Assad or his intentions.

“Anyone who uses chemical weapons to attack his own people shows a fundamental disregard for human decency and must be held accountable,” Tillerson said.

He also called on Iran and Russia to discourage the Assad regime from continuing such attacks.

“As the self-proclaimed guarantors to the ceasefire negotiated in Astana, Russia and Iran also bear great moral responsibility for these deaths,” the secretary added, referring to the Kazakh capital where the truce was hammered out.

Trump's comments directly contradict his past statements on Syria. In numerous tweets in 2013, he discouraged Obama from engaging in Syria and encouraged the United States not to act in response to Assad's brutalization of the Syrian people.

“President Obama, do not attack Syria. There is no upside and tremendous downside. Save your 'powder' for another (and more important) day!” Trump wrote in one message.

“The only reason President Obama wants to attack Syria is to save face over his very dumb RED LINE statement. Do NOT attack Syria, fix U.S.A.” he wrote in another message.