Ankara, March 16 (IANS): Turkey on Monday slammed a US suggestion that negotiations could be opened with Syrian President Bashar al-Assad for a political transition in the war-torn country, Xinhua news agency reported citing Turkish media.

"There is nothing left to negotiate with Assad and no outcome has been achieved so far from the talks with the Syrian regime," state-run Anadolu Agency quoted Turkish Foreign Minister Mevlut Cavusoglu, who is on a visit to Cambodia, as saying.

Cavusoglu's remarks came in response to a statement on Sunday by US Secretary of State John Kerry that his country was exploring ways to pressure Assad into agreeing to talks.

"What you will negotiate with is a regime that killed more than 200,000 people and used chemical weapons," Cavusoglu said.

Earlier, Kerry said that the US and other countries, which he did not name, were exploring ways to "reignite" the diplomatic process to end the Syrian crisis.

Turkey, once an ally of Assad, is now the fiercest opponent of the current Syrian government and has been supporting the opposition trying to topple the Syrian president since 2011.

Turkey declared the Syrian administration as illegitimate and conditioned any resolution of the crisis to the ouster of Assad from power.