Fallon's comments followed U.K. Secretary of State for Foreign and Commonwealth Affairs Boris Johnson's cancelation of his trip to Moscow over the chemical gas attack on civilians in Idlib, Syria and the US airstrike against the Syrian regime that followed Thursday.
Bashar Assad also thanked the Iranian leadership and the people for their continued support of the Syrian people in the face of the terrorist war which is backed by many Western and regional states.
Boris Johnson decided not go to Russian Federation amid growing pressure on President Vladimir Putin to cut his ties with Syria's Bashar al Assad in the wake of a suspected chemical attack that killed at least 87 people, including children.
Iranian President Hassan Rouhani on Sunday condemned as "flagrant US aggression on Syria" a USA missile strike on a on a Syrian air base this week and criticised Gulf Arab states for supporting it, state television reported.
"In the past few years, they have had every opportunity to pull levers and stop this civil war".
Before Tuesday's attack on the rebel-held town of Khan Sheikhoun, which killed 89 people, Haley had said toppling Assad was not a priority. Moscow has been a steadfast ally of the Syrian government and has defended it against claims of chemical weapons use in front of the U.N. Security Council.
Mr Tillerson will go ahead with his visit to Russian Federation to deliver a "clear and coordinated" message to Moscow, which continues to deny Syrian forces used chemical weapons last week.
Syria: What led to the USA air strikes?
But Sir Michael said the launching of nearly 60 missiles at the regime airbase from which the attack is said to have originated would now make future incidents less likely.
The SNP's foreign affairs spokesman said the move makes Mr Johnson look like "some sort of mini-me" who can not be trusted to hold his own talks with Russian counterpart Sergey Lavrov. Turkey provides military support to some of Syria's opposition forces.
But he said Turkey could not "remain silent" on the Syrian government's chemical weapons use, and insisted Moscow work with Ankara to establish a transitional government in Damascus.
British Foreign Secretary Boris Johnson cancelled a visit to Moscow, scheduled for April 10, after the poison gas attack in Syria.