Pro-reform supporters protest outside the Arab League headquarters in the Egyptian capital Cairo on November 24, 2011.

Story highlights

NEW: At least 35 people have died in violence Thursday, an activist group says

The Arab League could impose economic sanctions Sunday if Syria ignores deadline

Syria is under international pressure to halt its crackdown on pro-democracy protesters

The United Nations says more than 3,500 have died since the protests began in March

CNN  — 

Syria has until Friday to agree to let Arab League observers into the country to monitor the government’s response to civil unrest or else face economic sanctions from its neighbors, a senior Arab League diplomat said Thursday.

Syria’s membership in the 22-country Arab League was suspended this month after President Bashar al-Assad’s regime ignored demands to end its crackdown on citizens.

“If they do not comply, then the league’s economic body will file a report to the foreign ministers of the league who will meet on Sunday to vote on the economic sanctions to be implemented,” said the diplomat, who asked not to be named due to the sensitivity of the negotiations with Syria.

If Syria agrees by the Friday deadline, then the league will send a delegation to Damascus to discuss details of the observer mission before the team goes, the diplomat said.

At least 35 people died Thursday in clashes with security forces, the Local Coordination Committees of Syria (LCC) activist group said.

Another activist group, the London-based Syrian Observatory for Human Rights, reported earlier that at least 11 Syrian military defectors were shot dead and four injured during clashes with regular Syrian army units in the area. A further 73 civilians were arrested in Homs province Thursday, the group said.

A campaign of raids and arrests is also taking place in the Damascus suburb of Domeir, the Qalet Mudeeq neighborhood in Hama, and Baniyas, the LCC said.

Funerals were held Thursday for 12 army, police and security forces personnel, the state-run Syrian Arab News Agency reported. The 12 had been targeted by “armed terrorist groups” while on duty in the Damascus, Homs and Hama areas, the news agency said.

The United Nations says more than 3,500 people have been killed in the government’s eight-month crackdown on pro-democracy protests.

Al-Assad has resisted mounting calls for his resignation as president in recent weeks as international outcry over the Syrian violence has intensified.

On Tuesday, the humanitarian committee of the U.N. General Assembly voted by a large majority to condemn the violence in Syria and express its support for the Arab League initiative.

It was the first resolution on Syria’s crackdown to be approved at the United Nations.

Protesters in Syria are demanding al-Assad’s ouster and democratic elections. He has been in power since 2000, following his father, Hafez, who ruled Syria for three decades.

Syria’s government has said it is fighting armed terrorists, and it maintains that the death toll is much lower than international observers and opposition groups say.

CNN’s Lonzo Cook and Tracy Doueiry contributed to this report.