European Union foreign ministers have agreed to toughen sanctions against Zimbabwe's President Robert Mugabe to pressure him to share power with the opposition, diplomats said Tuesday ahead of the opening of talks between Zimbabwe's ruling and opposition parties in South Africa.

EU ministers agreed to expand their sanctions blacklist of people linked to Mugabe's government, the diplomats said on condition of anonymity because they were not authorized to speak to the media.

Bitter rivals Mugabe and opposition leader Morgan Tsvangirai agreed Monday to formal talks about sharing power to end Zimbabwe's crisis, deepened by three months of state-sponsored electoral violence. The talks were expected to begin later Tuesday at a secret location.