The Arab League has given Syria an ultimatum and only 24 hours to decide between allowing observers into the country or facing harsh economic sanctions that would see the freezing of assets and the stoppage of all financial dealings.

Meeting in Cairo on Thursday, the pan-Arab body's threat against Damascus -- a founding member of the Arab League -- was the third deadline given to Syria's government in three weeks. Earlier this month, the 22-member Arab League suspended Syria's membership over the unending bloodshed and Syria's failure to comply with a peace plan it signed with the League; the League is also considering imposing economic and political sanctions on Syrian President Bashir al-Assad's government.

The move comes amid growing international efforts to quell al-Assad's brutal and bloody crackdown on an uprising against his government. According to the United Nations, at least 3,500 people have been killed since mid-March.

Damascus had until Friday to agree to let an observer mission in. Otherwise, the Cairo-based Arab League will meet Saturday to decide sanctions, The Washington Post reported. Punishment could include ceasing trade with the Syrian government (apart from strategic goods that affect the Syrian people), stopping flights to Syria and ending deals with Syria's central bank, a committee statement said.

Thursday's meeting took place in a hotel rather than at the League's headquarters in the central Tahrir Square, the flashpoint where clashes between Egyptian security forces and protesters have occurred repeatedly.

On Wednesday, the United States Embassy in Damascus urged its citizens to depart Syria immediately, and Turkey's foreign ministry likewise beseeched its citizens to find return flights home through Saudi Arabia in order to avoid the mounting pandemonium going on in Syria.

The U.S. Embassy continues to urge U.S. citizens in Syria to depart immediately while commercial transportation is available, a statement posted on the Embassy's Web site and issued to the American community in Syria said Wednesday.

The number of airlines serving Syria has decreased significantly since the summer, while many of those airlines remaining have reduced their number of flights.

The warning followed an announcement in Washington this week that Ambassador Robert Ford would not return to Syria this month as planned, indicating concerns over his safety as Syrian President Bashir Assad continues to ignore increased international pressure to cease a brutal crackdown on his people, The Associated Press reported.

Citing credible personal threats, President Barack Obama and his administration quietly pulled Ford out of Syria last month.

The warnings from the U.S. and Turkey come as Syrian security carried out raids in the rebellious areas in the center and the south of the country on Wednesday, where at least six people died, bringing the two-day death toll to 34, activists said.

Two activist groups, the British-based Syrian Observatory for Human Rights and the Local Coordination Committees, documented the deaths of at least six people who were reported killed on Tuesday in the central cities of Hama and Homs, and in the eastern city of Deir el-Zour.

Protection of civilians in Syria is an increasingly urgent and important aspect of responding to the events in the country, Maja Kocijancic, an EU spokeswoman, said in a statement.

Arab diplomats said the league intends to isolate al-Assad from his supporters without causing harm to a population already starting to suffer from U.S. and European sanctions, The Wall Street Journal reported.

The Arab League has never done anything like this in its 66-year history, said Salman Shaikh, director of the Brookings Doha Center think tank.

In its totality, the league has helped push the sanction regime along and helped push multilateral pressure.