A LOOK AT AMERICAN INVOLVEMENT IN SYRIA

The US has largely avoided wading directly into the Syrian conflict or confronting President Bashar Al Assad and his allies throughout the seven-year war. In the early years of the Syrian conflict, Washington was part of a regional and western coalition that backed and armed vetted opposition groups who were fighting to topple Mr Al Assad. As ISIS captured areas across Iraq and Syria in 2014, the US began air strikes against the group. Here is a look at significant times when US forces used air and missile strikes to expand their role in Syria beyond the fight against ISIS:

February 7, 2018: The US military launches rare air strikes and artillery rounds against Syrian government-backed troops after up to 500 attackers started an attack on US-backed Syrian forces and US advisers in eastern Deir Ezzor province. US officials said the strikes were in self-defence after pro-government forces began firing artillery and tank rounds at the US-backed Syrian Democratic Forces. About 100 of the attackers were killed,.

June 18, 2017: US warplanes shoot down a Syrian air force jet, the first such incident. The Syrian SU-22 bombed US-allied forces fighting ISIS militants west of Raqqa city. American officials said they acted to defend allies attacked by the Syrian government as both rival forces raced towards Raqqa city.

June 8: US officials say US jets shot down an armed Iranian drone that had fired on US troops in southern Syria near a base where the international coalition against ISIS is training Syrian rebel forces. The missile did not detonate. US officials called it a direct threat to the coalition, and it came hours after an earlier attack by pro-government forces in the same area.

June 6: US air strikes hit pro-Syrian government forces who approached a camp in southern Syria where US-backed Syrian and American advisers were training. It was the second such confrontation between US forces and pro-Syrian government forces in less than three weeks. US officials described the forces as Iranianallied. US officials said air strikes destroyed two artillery pieces and an anti-aircraft weapon, and damaged a tank.

May 18: A US air strike hits pro-Syrian government forces who the coalition said posed a threat to American troops and allied rebels near the border with Jordan in southern Syria. It was the first such close confrontation between US forces and fighters backing Mr Al Assad. US officials said the air strike hit pro-Syrian government forces as they were setting up positions near Tanf and the border with Jordan. They said a tank and a bulldozer were also hit.

April 6: In retaliation for a government chemical weapons attack in northern Syria that killed nearly 90 people, including 31 children, the US fires 59 Tomahawk missiles at the government-controlled Shayrat airbase in central Syria. US officials said the Syrian military planes that dropped the chemicals had taken off from there, and claimed all but one of the missiles struck their targets, hitting aircraft and air shelters, and destroying the fuel area.

September 17, 2016: A coalition air assault killed more than 90 Syrian government troops in Deir Ezzor. The US said it was human error, because it was attacking what it thought were ISIS positions.