A United States military attack on a Syrian airfield in Homs province is a clear message that Washington is supporting "terrorists" trying to take over the country, a top Syrian official has said.

The US strike on the Shayrat air base on Friday followed international condemnation over a suspected chemical weapons attack earlier this week that killed dozens of people, including many children, in the rebel-held town of Khan Sheikhoun in Idlib province.

Homs Governor Talal Barazi said the US army's direct military involvement in the country's long-running conflict would not impact the government of Syrian President Bashar al-Assad or its ability to fight "terrorists".

"We knew from the beginning that this conspiracy against Syria has means and that ISIL, al-Nusra and others are means of American, Israel and other Arab regimes," Barazi told local media.

"We are not surprised today to see the supporting parties interfering directly after the failure of terrorists in targeting Syria," he added.

"We will not be surprised to see the Americans playing direct role on the ground to support its means everywhere."

Conversely, a Syrian opposition group welcomed the strike, saying Washington's direct military involvement could be an "opportunity to end" the war, now in its seventh year.

"We welcome these strikes," Najib Ghadbian, special representative of the Syrian National Coalition to the United States and the United Nations, told Al Jazeera.

"They are first good steps but we would like them to be part of a bigger strategy that would put an end to the mass killing, an end to impunity and eventually we hope that they will lead to a kind of a political transition [in Syria]."