By Michael O’BrienThe BBC’s Syria correspondentMichael O’Briain is reporting from the capital, Damascus, where he says it is difficult to tell what’s happening on the ground.
The conflict in Syria has been raging for three years and has killed nearly 400,000 people, driven millions from their homes and devastated many of its neighbours.
The war in Syria was started as a protest movement against President Bashar al-Assad, who took power in a military coup in 2011.
But it is now in its fifth year and is expected to continue for years.
The BBC has been reporting on Syria from its Syrian base in Beirut.
What you need to know about the conflict in the Middle East:Syria’s civil war is one of the most complex conflicts on the planet.
It has been waged in Syria since the country was recognised by the United Nations in 1963.
Since then, a number of countries have been supporting Syrian President Bashar Assad’s government, while others have offered humanitarian aid.
Mr O’Brannan says Syria’s neighbours are worried that a repeat of the unrest that swept through Lebanon, which has been hit by sectarian violence for years, could break out again.
The Lebanese civil war erupted in 2006 and has raged for almost two decades.
Syria is a predominantly Sunni Muslim country, and many of the population have fled the country.
Many people in Lebanon believe that Mr Assad’s regime is responsible for the conflict.
The Syrian government says the unrest is an attack by foreign agents and accuses the Syrian rebels of trying to overthrow it.
Mr Assad says his government is fighting terrorism, which it says is backed by foreign powers.
Syrian authorities accuse the Syrian rebel groups of arming the insurgents.
The US says it has limited air support for Syrian opposition fighters, and the Syrian government has repeatedly accused the US of sending arms to the rebels.
In recent weeks, a series of strikes by the US and its allies have hit targets in Syria, killing hundreds of people.
What the BBC has learned about the Syrian conflict in six key places:What we know about Syria:In September last year, the UN Security Council approved a deal to send in UN observers to monitor the ceasefire in Syria.
But Syria’s government and rebels have been at odds over how to conduct the mission, which could see the inspectors from the International Syria Support Group (ISSG).
The Syrian opposition said it was still waiting for the ISSG to be approved by the UN, which is expected in the coming days.
Mr Obama has said the mission will be “the most comprehensive and effective peacekeeping mission ever” but opposition members say it will not go far enough.
Syria’s government has been waging an increasingly brutal war against its neighbours since 2011, when it launched a military offensive that has killed thousands and displaced millions.
The fighting has also killed more than 4,000 civilians, according to the UN.
Syrian forces have been blamed for some of the worst abuses of the war, including torture, rape and killing civilians, as well as the kidnapping of hundreds of civilians, and thousands of others are suspected of having been killed.
What we learned about Syria from the UN’s chief:What you needed to know on the Syrian civil war:Syria has been the site of some of Syria’s worst atrocities, including a 2013 air strike by the coalition of countries led by Russia which killed hundreds of Syrians.
But Mr Assad has not been able to crush the insurgency, and has been fighting back.
The country has suffered more than 100,000 deaths, more than half of them civilians, since 2011.
What our experts are saying about the Syria conflict:The BBC and the Pulitzer Centre on Crisis Reporting are using data from Syria’s National Council for Human Rights to report on the conflict, as it unfolded.