The White House is standing by President Obama's decision to negotiate a deal with Syrian President Bashar Assad to relinquish his chemical weapons in the face of new evidence that Assad still has nerve agents.

Obama's top spokesman, Josh Earnest, told reporters Wednesday that the Organization for the Prohibition of Chemical Weapons is looking into evidence that Assad has retained chemical weapons after pledging to eliminate them.

"Obviously, this is something that the OPCW has been carefully looking at, and we believe that they should," Earnest said.

He then defended the U.S.-Russian-brokered deal with Assad aimed at ridding Syria of chemical weapons, arguing that it "made the world safer."

"It eliminated a significant amount of proliferation risk," he said.

"When you have a country overrun by extremists," he added, "it's not a good combination" to have an abundance of chemical weapons in the same area.

After Assad crossed Obama's "red line" by using Sarin gas on civilians in 2013, Obama decided against ordering U.S. military strikes against the regime and instead brokered a deal with the help of Russia to destroy or move all chemical weapons the regime possessed.

U.S. and European inspectors have repeatedly found traces of nerve agents in Syrian labs and have impugned the government's explanations for the findings as "not scientifically or technically plausible," according to a story Tuesday in Foreign Policy, which quoted a confidential report.

Earnest also told reporters Wednesday that the "situation in Syria has been murky for quite some time."

"We have expressed our previously long-running concerns about the gratuitous violence," he said, as well as reports that the Assad regime has weaponized chlorine gas and use it against civilians.

Such reports, he said, are "of deep concern to the United States and the international community."