"The success of the Annan plan depends on the end of terrorist acts and those who support them and the smuggling of weapons," Assad was quoted as saying.
States that "harbour and arm terrorist groups" should comply with the Annan plan, Assad added as he met with the envoy in Damascus, after 108 people were massacred at the weekend in what human rights groups accused the regime of carrying out.
Damascus has denied responsibility for the Houla massacre, blaming foreign-funded "terrorist groups" instead.
Annan arrived on Monday for talks with Assad, the opposition and representatives of civil society.
In his meeting with Assad on Tuesday, Annan conveyed "the grave concern of the international community about the violence in Syria, including in particular the recent events in Houla," his office said.
"He conveyed in frank terms his view to President Assad that the six-point plan cannot succeed without bold steps to stop the violence and release detainees, and stressed the importance of full implementation of the plan."
The UN human rights agency said most of the victims of the massacre were executed, and cited local residents as attributing responsibility to pro-regime paramilitary groups.
"According to local witnesses and survivors who have been interviewed, most of the rest of the victims in Taldu, one of the areas of Houla, were summarily executed in two separate incidents which local people are attributing to a shabiha paramilitary group," spokesman Rupert Colville said. (*)
Editor: Kunto Wibisono
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