The Obama administration is determined to avoid a repeat of the aftermath of the American invasion of Iraq. Though the United States did not stint in its effort to oust Saddam Hussein, many foreign policy experts now say that the undertaking came at the expense of detailed planning about how to manage Iraq’s warring factions after his removal.

Syria is sure to be discussed when President Obama meets Tuesday with Prime Minister Recep Tayyip Erdogan of Turkey on the periphery of the United Nations General Assembly meeting in New York, administration officials say. A senior administration official said the abandonment of Mr. Assad by Turkey, Saudi Arabia and European nations would increase his isolation, particularly as his military became more exhausted by the lengthening crackdown.

Another Obama administration official said that with 90 percent of Syria’s oil exports going to Europe, shutting the European market to Damascus could have a crippling effect on the Syrian economy and could put additional pressure on Mr. Assad’s government.

“Back in the 1990s, if Syria wanted credit and trade and loans that they couldn’t get from the United States, they went to the Europeans,” said Ray Takeyh, a senior fellow for Middle Eastern studies at the Council on Foreign Relations and a former Obama administration official. Now, Mr. Takeyh said, Europe has joined the United States in imposing sanctions on Syrian exports, including its critical oil sector.

Aside from Iran, he said, Syria has few allies to turn to. “The Chinese recognize their economic development is more contingent on their relationship with us and Europe than on whether Assad or Qaddafi survives,” he said, referring to the deposed Libyan leader, Col. Muammar el-Qaddafi.