A United Nations Security Council resolution will help put added pressure on Syrian leader Bashar Assad to end the crackdown on protesters in Syria, United States State Department spokesman Mark Toner said on Wednesday.

Toner was referring to an earlier announcement by British Prime minister David Cameron, saying that Britain and France will put forward a UN resolution condemning Syria's crackdown.

“We support pursuing a UN Security Council resolution regarding the ongoing situation in Syria, and we're advocating and trying to convince others on the council to do the same." Toner said.

"We believe that such a resolution will bring added pressure on Assad's regime and advance the international community's efforts to end the brutal repression of the Syrian people."

Britain, France, Germany and Portugal circulated a draft resolution condemning Syria at the UN Security Council last month, but diplomats say Britain has been working on a version with tougher language. Veto powers Russia and China have made clear they dislike the idea of council involvement.

Toner said a UN resolution would "add to the mounting international condemnation of what's been going on in Syria and help build a broader coalition, if you will, towards ending the violence and pressuring Assad to make the right decisions."

European Union nations are also preparing a fresh round of sanctions against Syria that target Syrian companies, a senior European diplomat told reporters on Wednesday.

The diplomat, who spoke on condition of anonymity, said the the additional sanctions were part of a concerted effort to increase pressure on Assad's government to end the crackdown on pro-democracy demonstrators.

"We are working on a third round of sanctions that would target companies, the economic sector," the diplomat told reporters.

The EU has already passed two rounds of sanctions against Syria this year. The first imposed travel restrictions and asset freezes on up to 13 Syrian officials for their part in the crackdown but excluded Assad.

The second round added Assad and nine other senior members of the Syrian government to the travel bans and asset freezes.

Toner said that the U.S. also has sanctions in place against Syria. He explained the sanctions and the potential UN resolution as part of a "broader effort to build pressure on Assad and to make it very clear to him and his regime, that they need to stop the violence and to meet the aspirations of the Syrian people in a meaningful way and reform."

"And until we see that, we're going to keep adding pressure," Toner said.