Germany and other Western powers have repeatedly called on Assad to step down to put an end to protests against his government, which have triggered a violent backlash from his security forces.Syrian security forces have killed more than 5,000 people in the past year, according to human rights groups, while the Assad government says more than 2,000 soldiers and security agents have been killed.
"We will adopt further sanctions in Europe, and not just in Europe," Westerwelle told Reuters in an interview on the sidelines of a meeting of foreign ministers from the Group of 20 economic powers in Los Cabos, Mexico.
"I believe sanctions will be tightened in the next week, because the violence is continuing," he said, when asked whether Europe would adopt measures to blacklist Syria's central bank.
Westerwelle declined to name specific sanctions under consideration, but a G20 official at the meeting, speaking on condition of anonymity, said the EU was on course to agree to measures to curb the central bank's ability to operate.
EU diplomats said this month they were working on a new round of sanctions against Syria, which they hope to finalize by February 27. These would include a freeze on the Syrian central bank's assets as well as on most transactions with it.
Westerwelle said it was time to raise diplomatic pressure against Syria, and received support from the United States and Britain in Mexico, who also urged China and Russia to do more.