Mr Hague’s comments came before EU foreign ministers agreed to tightens sanctions and enforce an arms embargo against President Bashar al-Assad’s regime.
Member states endorsed the measures on Monday and also added 26 Syrian individuals and three companies suspected of financing the Syrian government to the bloc’s existing sanctions list.
The agreement in Brussels came as government forces fought back against Syrian rebels after one of the bloodiest weeks in the 16-month uprising against Assad’s rule.
Whilst fighting continues in the city of Aleppo, rebels in Damascus have been driven back by security forces after a sustained campaign in the capital last week.
On Monday Syrian state TV showed footage of government forces going house to house and kicking down doors in the capital, searching for any remaining rebel fighters, after recapturing the suburbs of Barzeh and Mezzeh, which had fallen into the hands of anti-regime fighters.