Following an alleged chemical attack in Syria, the United States President, Donald Trump, Sunday, blamed former President Barrack Obama.

“If President Obama had crossed his stated Red Line In The Sand, the Syrian disaster would have ended long ago! Animal Assad would have been history!” President Trump tweeted, referring to Syrian President Bashar Assad.

Obama said last year that he believed his decision to negotiate rather than respond with force to Syria’s use of chemical weapons required some of the greatest “political courage” of his presidency.

That was despite Obama saying in 2012 that if Assad used chemical weapons it would cross “a red line” with the U.S. The United Nations accused Syria of using chemical weapons on its own people in 2013.

“You generally get praised for taking military action, and you’re often criticized for not doing so,” Obama said last May.

Dozens died and hundreds were reported injured Saturday in an alleged chemical attack in Syria, reports The Hill.

State Department spokesperson Heather Nauert said in a statement that U.S. officials are closely following the “disturbing reports … regarding another alleged chemical weapons attack, this time targeting a hospital in Douma, Syria.”

The U.S. is calling on Russia to end its support for Assad.

Damascus has denied responsibility for the attack, Reuters reported.

Trump administration officials told The Associated Press in February they believed forces loyal to Assad might have been in the process of working on new, or more refined chemical weapons.

Trump said last year that reports of a deadly gas attack by forces loyal to Assad had “crossed a lot of lines.”