A policeman walks in front of the damaged U.S. embassy after pro-government protesters attacked the compound in July. The embassy will be shuttered unless the embattled regime provides enhanced protection. (AP)

The Obama administration is preparing to evacuate American personnel and close the U.S. embassy in Damascus, Syria, by the end of this month unless the embattled government of Syrian President Bashar al-Assad provides additional security for the facility, senior administration officials said.

Officials said they have not reached a final decision and are engaged in talks with the Assad government, but there so far have been no tangible results in providing more protection for the embassy.

“We have serious concerns about the deteriorating security situation in Damascus, including the recent spate of car bombs, and about the safety and security of embassy personnel,” a State Department release Friday evening said. “We have requested that the government of Syria take additional security measures to protect our embassy, and the Syrian government is considering that request. We have also advised the Syrian government that unless concrete steps are taken in the coming days we may have no choice but to close the mission.”

A drawdown of the staff at the embassy, which is located on a busy street in Damascus, began last week after three unexplained car bombings in recent weeks jarred the previously calm capital and left as many as 80 people dead.

Government claims that al-Qaeda was responsible for the recent attacks were widely scorned by activists who accused the government itself of responsibility. Although the administration has not ruled out Syrian government involvement in the attacks, U.S. officials said signs point to Syrian and Iraqi militants that have been affiliated with al-Qaeda.

“It smells like a terrorist attack and looks like a terrorist attack, but none of us knows for sure,” said a senior Obama administration official, who spoke on the condition of anonymity in discussing the sensitive situation.

Officials declined to discuss whether there have been specific threats to the embassy, and they would not describe the nature of the security measures they are seeking from the Assad government. But the suicide car bombings, the official said, “have brought the situation in Syria to another level.”

If even a small number of Sunni extremists from Iraq have become involved in the Syrian conflict, it would add an alarming new dimension to what has been an overwhelmingly peaceful uprising that has been brutally attacked by the decades-old dictatorship.

Many Syrian opposition activists already are concerned about signs of a creeping Islamization of the revolt, and they have warned that the failure of the West to intervene will open the door to Islamists, threatening the kind of destabilization that took hold in Iraq following the U.S. invasion there.

The senior administration official said that the deteriorating security situation across Syria “demonstrates further that Assad is losing control of the country and reinforces our point that Assad has lost all legitimacy.”

Officials said U.S. concerns were shared by other Western and Arab embassies in Damascus, and that many had joined the United States in drawing down their staffs over the past week.

By explicitly warning that the embassy may close, the Obama administration appeared to be signaling Assad that its patience is running out.

U.S. ambassador Robert Ford was forced to leave Syria in October after receiving direct threats associated with regime supporters. He returned last month, after administration officials assessed that the threat had abated. Officials emphasized the importance of maintaining direct contact with opposition leaders and providing the opportunity of real-time reporting from Damascus.

On Friday, which has been the biggest day of the week for anti-government protests, Damascus felt as though it was under siege. Soldiers sealed off several major roads and checkpoints dotted the city. Outside one of the main offices of the security branches, there were sandbagged machine gun positions. Soldiers wearing flak jackets and holding machine guns kept guard.

A lone policeman with a Kalashnikov slung across his shoulder stood across the street from the main entrance to the U.S. embassy. There were also several soldiers and policemen dotted around the nearby traffic circle, but no more than at any other intersection.

Near the scene of the most recent bombing, outside the Zain Abeddine mosque in the neighborhood of Midan, hundreds of soldiers, police and plainclothes men belonging to what is known as the “shabiha” militia were out in force to prevent the eruption of protests after Friday prayers. Men streamed out of the mosque under their watchful eye, and only one small group dared break into chants of “God is great” before they were quickly dispersed by the security forces.

Fearful merchants nearby said the overwhelming presence of security forces since the bombing had deterred all but a few protests in recent weeks. The attack had also kept customers away.

“Everyone is afraid,” said one man selling pastries in a small shop. “Business is down below zero. No one knows what will happen next. Maybe there will be more bombings. Anything could happen.”

Sly reported from Damascus.