Iran's Foreign Minister Mohammad Javad Zarif met embattled Syrian President Bashar al-Assad in Damascus on Wednesday, and called on regional countries to "fight terrorism and extremism".

"I say to the other (regional) players and to our neighbours that now is the time to care about the truth, answer the aspirations of the Syrian people and work to fight terrorism, extremism, and sectarianism," the top diplomat said.

He did not give details on his discussions with Assad on finding a solution to Syria's four-year war, only describing the exchange of views as "good".

An Iranian foreign ministry spokesman had said a new Iranian peace plan was based on "respect for the Syrian people's legitimate right to reforms and to decide their own future".

Zarif arrived in Damascus on Wednesday after morning meetings in Beirut with officials including his Lebanese counterpart Gebran Bassil.

"We are ready to cooperate, exchange ideas, and work together with these nations to fight extremism, terrorism, and sectarianism," Zarif said at a news conference in Beirut.

"We hope that the people of this region and the Lebanese people will benefit from this cooperation."

Late Tuesday, Zarif met Prime Minister Tammam Salam and Hassan Nasrallah, head of the Lebanese Shiite group Hezbollah.

Iran, Hezbollah and Russia have been the biggest backers of the Assad regime throughout the deteriorating conflict.