Secretary-General Ban Ki-moon is criticizing Syrian President Bashar Assad for failing to halt a military crackdown on dissent that has killed nearly 2,000 people.
Ban says Assad pledged to him by phone on Wednesday that all military and security operations would end.
"It is troubling that he has not kept his word," the U.N. chief told reporters Monday.
The secretary-general says many world leaders have urged Assad to end the violence.
Ban added: "I sincerely hope that he heeds the international community's appeal."