New United Nations-Arab League envoy Lakhdar Brahimi will meet with Syrian President Bashar al-Assad when he makes first official visit to Syria this week.

U.N. chief Ban Ki-moon gave no details of Brahimi's visit or whether he expected progress in ending the bloody 18-month rebel uprising against the Assad government.

Brahimi said earlier this week that his task will be difficult. But said he will try his best to give as much help as possible to the Syrian people. He said the Syrian people will be his only “master” while in Damascus.

Brahimi replaces former envoy Kofi Annan, who failed to reach a ceasefire in Syria and open talks on a transitional government.

U.N. officials say the fighting in Syria has killed about 20,000 people, nearly all of them civilians, and driven more than one-million from their homes.

More than 250,000 civilians have fled to refugee camps in Jordan, Iraq, Lebanon, and Turkey. The U.N refugee agency calls the humanitarian problems caused by the war its biggest crisis.

Agency spokeswoman Sybella Wilkes told VOA the numbers are increasing “by the thousands every day.” She said UNHCR's two main priorities are for neighboring countries to keep their borders open and for a “dramatic increase” in international support to facilitate the effective accommodation of refugees. Wilkes described the conditions in Jordanian refugee camps — where 27,000 Syrians are living in tents — as “unacceptable.” She warned that the searing heat of summer will soon give way to harsh winter weather.

Also Tuesday, activists said Syrian troops pounded the northern city of Aleppo to thwart a rebel advance. Violence and bloodshed were reported in other parts of Syria.