Damascus 'manoeuvring'
The Arab League's Secretary General, Nabil al-Arabi, told reporters that an advance party led by one of his assistants would travel to Syria in the next two or three days to prepare for the arrival of monitors.
The observers will have a one-month mandate that can be extended by another month if both sides agree.
But the leader of the Syrian National Council, an opposition umbrella group, dismissed the government's decision as "just a ploy".
The BBC's Jim Muir in Beirut says there is much scepticism in activist circles about the government's willingness to implement a peace plan which could result in large parts of the country falling out of its control.
Since mid-November, Syria wavered on whether to agree to the deployment of observers, prompting the Arab League to impose a range of economic sanctions.
In that time, more than 900 civilians have been killed by Syrian security forces, including 80 children and 29 women, according to the LCC.