BEIRUT, Lebanon — With tanks now patrolling the streets of a restive Syrian city, the Obama administration is preparing to take its first concrete steps against President Bashar Assad and his top lieutenants – the imposition of sanctions for an increasingly bloody crackdown on demonstrators.

The regime in Damascus escalated the violence Monday, ordering army tanks and troops into action against protesters in the southern city of Daraa. The move follows a tumultuous weekend in which Syrian security forces gunned down an estimated 120 pro-democracy protesters. More than 200 people have died since the uprising erupted five weeks ago.

Obama administration officials said they are readying orders that would freeze U.S. assets of senior Syrian officials and deny them permission to travel in the United States.

U.S. sanctions are unlikely to produce a dramatic impact because Syrian officials apparently own few U.S. assets. But the move signaled a notable shift by the Obama administration, which has worked hard to build better relations with Damascus, a regime it considers a strategic key for security in the Middle East.

European officials said they also are considering steps against Assad’s regime. Syrian officials maintain far larger investments in Europe than in the U.S., so economic sanctions or travel bans there would have a more direct impact.

Officials in Washington have consulted closely with their counterparts in France and Britain on how best to persuade Assad to show restraint.

David Schenker, a former Middle East adviser at the Pentagon, said steps to isolate Syria, especially by European countries, would sting.

Even though he took over from his father a decade ago and has maintained Syria’s authoritarian system, Assad has cherished the idea that he retains “an international legitimacy and acceptability,” said Schenker, now an analyst with the Washington Institute for Near East Policy, a non-partisan think tank.

The administration has been ratcheting up its criticism of Assad’s response to the popular unrest, but Obama has yet to declare that Assad has lost the legitimacy to rule, according to The Washington Post.

“We very much see our role in these things as one that is behind what the voices in the region are saying,” said one administration official, who like others spoke on the condition of anonymity in order to describe internal thinking.

Administration officials say a majority of those taking part in Syria’s demonstrations have begun calling for Assad’s departure, an escalation of the movement’s initial demand for more civil rights and political freedoms under the existing government.

The tipping point may have come in the weekend of violence, giving Obama the cover he has sought before calling for regime change in the Arab world.

“We’re not there yet,” the administration official said. “This will be event-driven.”

Obama’s reluctance is rooted in fear of what might replace Assad, a member of Syria’s minority Alawite sect who is running a Sunni-majority country with a prevalent, if repressed, Islamist strain in its society and politics.

His secular Baath Party has been viewed by neighbors as a bulwark against Islamic extremism, making his government a linchpin in the volatile region. Many U.S. allies, including Israel, Saudi Arabia and Turkey, are hoping that Assad finds a way to remain in power.

In Syria, heavy-caliber gunfire crackled at dawn Monday as tanks rolled into Daraa, the flashpoint of the uprising. Amateur videos posted online appeared to show bodies in the streets as protesters came under fire from the tanks’ gunners and snipers on nearby roofs.

One report by activists said more than 25 people were killed “but no one could get close to them because of the brutal shooting.” The activists said a military force of between 4,000 and 5,000 men marched into Daraa along with up to a dozen tanks.

The regime’s ratcheting up of pressure was not limited to Daraa. At least 13 people had been killed since Sunday in the coastal city of Jebleh, activists said. Scores of people were reported arrested in the Damascus suburb of Duma. Gunfire was reported in Muadamia, another suburb. 

The Washington Post contributed to this report.