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The European Union is considering slapping more economic sanctions against Syria, including an embargo on oil, officials said Friday.

A foreign policy committee is studying options for what would be the EU's fifth set of sanctions against President Bashar Assad's regime, spokesman Michael Mann said. Human rights groups claim Assad's forces have killed nearly 2,000 people since mid-March.

An EU oil embargo would be in line with the latest U.S. moves to isolate the regime, including a ban on the import of Syrian petroleum or related products.

Syria gets about 28 percent of its revenue from the oil trade, with exports going mostly to European countries, such as Germany, Italy and France. If the EU joins the effort, it could significantly slash the Damascus government's revenues.

The EU has already imposed travel bans and asset freezes against 35 Syrian government officials and military and police commanders, including Assad himself.

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Mann said diplomatic representatives of the bloc's 27 member states were looking into adding more individuals and enterprises to the list, but declined to elaborate further.

"A number of economic sectors may possibly be added, and that includes oil," he said.

In the past, the EU has been reluctant to restrict Syrian oil and gas exports for fear that shortages might hit the Syrian public and small businesses.

Some EU nations have been lobbying for other sectors to be added to the sanctions regime, including telecommunications and banking.

In coordinated statements on Thursday, President Barack Obama and the leaders of Britain, France, Germany, Canada and the EU all called for Assad to resign, saying his repression of demonstrations inspired by this spring's Arab uprisings made him unfit to lead.

The calls were the first explicit demands for Assad to step down.

But on Friday, Russia said it opposes Western calls for Assad to resign.

The Interfax news agency reported that Foreign Ministry spokesman Alexander Lukashevich said Moscow believed Assad must be given sufficient time to fulfill promises of reforms.

He said Assad has already made some steps toward reform, including lifting the state of emergency and issuing a decree allowing peaceful demonstrations.

Russia's opposition will make it difficult for the U.S. and its European allies to get U.N. Security Council backing for their sanctions regime. Russian diplomats have said Moscow fears that any resolution condemning Syria could result in an all-out Western military attack on Syria similar to the bombing campaign against Libya, now in its sixth month.