Turkish Prime Minister Recep Tayyip Erdogan said on Thursday that there is no doubt that Syrian President Bashar Al-Assad has used chemical weapons against rebels.

Erdogan added that he would discuss the issue with U.S. President Barack Obama during his upcoming visit to Washington.

“We will discuss the use of chemical weapons during the meeting with President Obama. It is obvious that the al-Assad regime is using it,” Erdogan told the Japanese daily Nikkei in an interview.

“The opposition dominates on land, however Assad uses chemical weapons, war planes and helicopters. The only field the regime is superior in is air backed operations,” he added.

Erdogan predicted that “the regime is living its final moments but we don’t know when it will topple. This is a situation that will happen suddenly.”

Last week, the United States said for the first time that Syria had likely used chemical weapons against rebel forces, but emphasized spy agencies were still not 100 percent sure of the assessment.

In the past, President Barack Obama warned that use of chemical weapons by the Assad regime would cross a red line.

On Tuesday the president admitted there was evidence that chemical weapons had been used during Syria’s two-year conflict, but that it was not yet known how the chemical weapons were used, when they were used and who used them.

A defected general has confirmed that the Syrian government ordered the use of chemical weapons against the Free Syrian Army during select battles with Syrian regime forces.

The general, Zahir al-Sakit, told Al Arabiya that he disobeyed the orders and substituted the chemicals with disinfectant water he called “Javel water.”