The U.S. and European governments have begun to discuss whether to escalate sanctions against President Bashar al-Assad by targeting Syria’s oil industry. But European countries are wary about whether a boycott would work.

Officials on both continents are looking at stepped-up measures to pressure Assad as his government attempts to crush a four-month uprising led by pro-democracy youths. In recent weeks, Western governments have announced sanctions against Assad and some of his allies, but the continuing bloodshed has driven them to seek stronger measures.

The United States has little economic leverage on Syria, having cut off most trade years ago. The Europeans, in contrast, buy about half of Syria’s oil. France, Germany, Italy and the Netherlands are the biggest customers.

But some Europeans fear a boycott of the oil could backfire — possibly harming the Syrian population. In addition, experts say, the impact of a boycott could be blunted if countries such as China and India step in to buy the fuel.

“It’s not a watertight solution. Even if the EU and U.S. were able to initiate some kind of boycott of oil sales, it would be possible for the Syrian regime to find ways around it,” said Chris Phillips, a Middle East specialist at the Economist Intelligence Unit.

Supporters say the boycott is worth trying nonetheless. Sen. Mark Kirk (R-Ill.) and two other senators introduced a bipartisan bill this week that would penalize any company, including European firms, that invested in or purchased from Syria’s oil sector.

Kirk said the bill would send a message that “it’s best to start preparing, in your own business plans, to terminate or at least suspend operations” in Syria.

Oil exports are less important to Syria than they are to Iraq, whose petroleum sales were targeted in U.N. sanctions in the 1990s against then-President Saddam Hussein. Those sanctions were widely criticized for impoverishing ordinary Iraqis while failing to dislodge Hussein.

Syria’s petroleum exports of about 150,000 barrels per day make up less than one-fifth of Syria’s gross domestic product. But they account for one-third of government revenue.

“It will cripple the regime, but not kill society,” said Andrew Tabler, a Syria expert at the Washington Institute for Near East Policy.

“If these [sanctions] are implemented, does it immediately mean the regime stops killing? No,” Tabler added. “But does it mean several months from now the regime runs out of money? Yes . . . it affects their calculations significantly.”

Many Syrian opposition figures support some type of oil sanctions. Radwan Ziadeh, a leading dissident in exile, said that if the economy suffered briefly as a result, “the people there do not mind, if it brings down the regime.”

EU ambassadors meeting in Brussels on Thursday agreed to consider extending sanctions to the oil industry, but didn’t go further.

An oil embargo “is not something that is ruled out,” one European official said, speaking on the condition of anonymity under standard diplomatic practice. “We’re just trying to figure out what the consequences would be.”

But another European diplomat said the sanctions could inadvertently help Assad, who has tried to make the West a scapegoat for the shrinkage of the Syrian economy.

“At the moment, we can rebut that very effectively, by saying there were no sanctions against the country or the people, only this small number of individuals . . . and that the economic crisis facing the country is a direct and predictable result of the regime’s behavior,” said the diplomat, also speaking on the condition of anonymity.

The U.S. ambassador in Damascus, Robert Ford, said this week that the Obama administration was talking to Canadian and European governments about new sanctions on the oil industry.

The Obama administration slapped economic sanctions on Assad and several of his allies in May. On Thursday, it added a top businessman, Muhammad Hamsho, to the list.

Ford said the sanctions were starting to bite. “More and more business people, especially Sunni business people — an important pillar of the regime’s support — we do see them slowly but surely shifting sides,” he said.