In the process, he said, Mr. Assad had also probably disqualified himself as a peace partner for Israel. Such a prospect had seemed a long shot in any event — Prime Minister Benjamin Netanyahu has shown no inclination to talk to Mr. Assad — but the administration kept working at it, sending its special envoy, George J. Mitchell, on several visits to Damascus.
Mr. Assad has said that he wants to negotiate a peace agreement with Israel. But with his population up in arms, analysts said, he might actually have an incentive to pick a fight with its neighbor, if only to deflect attention from the festering problems at home.
“You can’t have a comprehensive peace without Syria,” the administration official said. “It’s definitely in our interest to pursue an agreement, but you can’t do it with a government that has no credibility with its population.”
Indeed, the crackdown calls into question the entire American engagement with Syria. Last June, the State Department organized a delegation from Microsoft, Dell and Cisco Systems to visit Mr. Assad with the message that he could attract more investment if he stopped censoring Facebook and Twitter. While the administration renewed economic sanctions against Syria, it approved export licenses for some civilian aircraft parts.
The Bush administration, by contrast, largely shunned Damascus, recalling its ambassador in February 2005 after the assassination of a former Lebanese prime minister, Rafik Hariri. Many Lebanese accuse Syria of involvement in the assassination, a charge it denies.
When Mr. Obama named Mr. Ford as his envoy last year, Republicans in the Senate held up the appointment for months, arguing that the United States should not reward Syria with closer ties. The administration said it would have more influence by restoring an ambassador.
But officials also concede that Mr. Assad has been an endless source of frustration — deepening ties with Iran and the Islamic militant group Hezbollah; undermining the government of Saad Hariri in Lebanon; pursuing a nuclear program; and failing to deliver on promises of reform.
Some analysts said that the United States was so eager to use Syria to break the deadlock on Middle East peace negotiations that it had failed to push Mr. Assad harder on political reforms.
“He’s given us nothing, even though we’ve engaged him on the peace process,” said Andrew J. Tabler, who lived in Syria for a decade and is now at the Washington Institute for Near East Policy. “I’m not saying we should give up on peace talks with Israel, but we cannot base our strategy on that.”
The United States does not have the leverage with Syria it had with Egypt. But Mr. Tabler said the administration could stiffen sanctions to press Mr. Assad to make reforms.
Other analysts, however, point to a positive effect of the unrest: it could deprive Iran of a reliable ally in extending its influence over Lebanon, Hezbollah and the Palestinians in the West Bank and Gaza.
That is not a small thing, they said, given that Iran is likely to benefit from the fall of Mr. Mubarak in Egypt, the upheaval in Bahrain, and the resulting chill between the United States and Saudi Arabia.
“There’s much more upside than downside for the U.S.,” said Martin S. Indyk, the vice president for foreign policy at the Brookings Institution. “We have an interest in counterbalancing the advantages Iran has gained in the rest of the region. That makes it an unusual confluence of our values and interests.”