President Bashar Assad’s grip on power has been increasingly threatened with the assassination of two of his top defence ministers in the capital Damascus.
His regime has also been hit by a series of military defections.
Mr Hague and Mr Ban are expected to discuss last week’s failure to agree a Security Council resolution at the UN, after Russia and China vetoed moves to ramp up the pressure on Assad.
Their meeting comes after Syria’s most prominent defector, Republican Guard commander Brigadier Gen Manaf Tlass, who fled Syria earlier this month, put himself forward as someone to unite the fractured opposition groups trying to topple Assad.
The factions met in Qatar yesterday to thrash out a deal over a transitional leadership.
Activists say 19,000 people have been killed since the uprising began last February as the Arab Spring pro-democracy uprisings swept the Middle East and North Africa.
Escalating civil war
Earlier this week, former army commander Colonel Richard Kemp, who led UK forces in Afghanistan, said the escalating civil war meant it was more likely western governments would intervene to stop the bloodshed spreading to neighbouring countries.
In a paper for the Royal United Services Institute, he said: “Western political leaders may have no appetite for deeper intervention.
“But as history has shown, we do not always choose which wars to fight – sometimes wars choose us.”
The summit comes less than 12 hours before the Olympics opening ceremony begins in east London – and Mr Hague and Mr Ban will trumpet the Olympic Truce, the spirit of bringing nations together and ending conflict through sport.
The idea goes back to the ancient Games in 9BC and the tradition was revived in 2000 in the run-up to the Sydney Games.
According to the Olympic Truce Centre’s website, “its mission is to promote the Olympic ideal, to serve peace, friendship and international understanding, and to uphold the Olympic Truce”.
The website continues: “It promotes a culture of peace through a combination of global and local initiatives, mobilising leaders, athletes and young people of the world behind the cause of sport and peace.”