EU foreign ministers are set to impose a travel ban and asset freeze on the UK-born wife of Syrian leader Bashar al-Assad, diplomats say.
Asma al-Assad is among 12 Syrians to be added to a number of figures, including the president, who are already subject to sanctions.
It was unclear whether the ban would stop her from travelling to the UK.
Anti-government activists accuse the regime of killing thousands of protesters over the past year.
In recent weeks, the Damascus government has stepped up its efforts to crush pockets of rebellion in cities including Homs and Hama.
Every day, activists report dozens of deaths and more protests.
Mr Assad has promised political reform, but observers and his opponents have dismissed his plans as window-dressing.
The BBC's Chris Morris in Brussels says for years there was a perception that Mrs Assad's Western upbringing could encourage reform in Syria.
The 36-year-old, who is of Syrian descent but spent much of her life in west London, has generally played a low-key role in the regime.
However, in February she wrote to Britain's Times newspaper to explain why she thought her husband was still the right man to lead Syria.
Last week activists released some 3,000 emails they said were from private accounts belonging to Mr Assad and his wife.
The messages, which have not been independently verified, suggested Mrs Assad continued to shop online for luxury goods even after the uprising was in full swing.
The UN says at least 8,000 people have died since the uprising against Mr Assad's regime began last March.
The president and his allies say terrorist and armed gangs are behind the violence, and say hundreds of security personnel have been killed fighting them.