JOHANNESBURG, South Africa — European Union foreign ministers agreed today to toughen sanctions against Zimbabwe’s President Mugabe to pressure him to share power with the opposition ahead of the opening of talks between Zimbabwe’s rival parties in South Africa.

Mr. Mugabe and the opposition leader, Morgan Tsvangirai, agreed yesterday 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 today at a secret location, a spokesman for South Africa’s president, Thabo Mbeki, who is mediating, Mukoni Ratshitanga, said.

The agreement includes a key opposition demand for an end to the political violence that has killed dozens, injured thousands and sent tens of thousands fleeing from their homes. Mr. Mbeki persuaded the parties to agree to complete negotiations within two weeks in a sudden show of urgency which may have been heightened by intense international pressure.

In Brussels, EU foreign minister agreed to expand their sanctions blacklist of people linked to Mr. Mugabe’s government to 172 people, adding 37 individuals and four companies believed to financially support Mr. Mugabe and his ZANU-PF party. The list already had 131 people, including Mr. Mugabe and members of his Cabinet, under measures passed in 2002.

The ministers said in a statement they decided to expand sanctions “against those responsible for the campaign of violence that marked the elections,” and vowed to take additional “appropriate measures” if Mr. Mugabe fails to hand over power to the opposition.

“We want there to be sanctions because sanctions have an effect,” France’s foreign minister, Bernard Kouchner, told reporters after the decision.

The EU ministers also concluded that Mr. Mugabe’s one-man June re-election in a presidential run-off vote was illegitimate. Mr. Tsvangirai withdrew because his supporters were being beaten and killed — was not legitimate. Mr. Mugabe insists he won the election but Mr. Tsvangirai says the only valid election was the March balloting in which he got the most votes.

“It is impossible to accept the second round of elections in Zimbabwe. With children being tortured, with barbarous acts being committed, with violation of basic democratic rules, we cannot allow this second round to be accepted,” Mr. Kouchner said.

The revised list is subject to a travel ban and assets freeze and its expansion was meant to keep the pressure on Mr. Mugabe to cooperate with Mr. Tsvangirai in the power-sharing talks.

The EU ministers also agreed to tighten a travel ban on Mr. Mugabe. Under new rules all member nations will have to approve a visit to an EU country before he would be allowed to enter the 27-nation bloc. Currently, only a majority needs to approve his visits.

In the past year, Mr. Mugabe has twice attended international events in Europe, circumventing the EU ban.

They EU also agreed to study further measures, notably on dissuading European companies from doing business with Mr. Mugabe’s government because of concerns he and his ministers are using businesses to move around their cash.

The 37 added names include military chiefs and a journalist from a pro-Mugabe newspaper. The companies added are those the EU believes are being used to back Mr. Mugabe’s ZANU-PF party, including a farm cooperative and ZANU-PF’s publishing arm.

The bloc also has in place a ban on arms sales.

The EU also welcomed the upcoming negotiations between the rival parties.

The British foreign secretary, David Miliband, said a face-to-face meeting between Mr. Mugabe and Mr. Tsvangirai yesterday was only “a first step,” and EU nations were expecting more proof that Mr. Mugabe was willing to sign up to a transitional government with the opposition.

“It requires an end to the violence, it requires an end to the ban on humanitarian NGO’s getting around Zimbabwe. Those are the first steps toward a resolution of the Zimbabwean crisis,” Mr. Miliband told reporters.

Beyond the political crisis, Zimbabwe’s economy is in ruins. Mr. Mugabe’s seizures of white-own commercial farms have destroyed the former food-exporting nation. One third of the population has fled the country, another third is dependent on food aid and some 80% are unemployed.

There are chronic shortages of fuel, medicine and food with daily cuts in power and water service and inflation has spiraled out of control to 2.2 million percent annually, the highest in the world.

Monday’s agreement between the parties gives broad outlines for discussion and no indication what Mugabe, who has clung to power for 28 years, may be willing to concede in talks with the opposition.

The leaders agreed on the need to work together “in an inclusive government” — the closest language to a power-sharing accord. And they committed to creating a “genuine, viable, permanent and sustainable solution.”

Tsvangirai, in an open message to Zimbabweans Tuesday, said the agreement “offers the most tangible opportunity in the past 10 years to improve the lives of our fellow citizens.” However, he cautioned “our signatures alone do not guarantee that we will be able to make the most of this opportunity.”

Mugabe said they must “chart a new way” — but act without influence from Europe or the United States. In the past, he has branded Tsvangirai a Western puppet.

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Michelle Faul reported from Johannesburg and Constant Brand reported from Brussels.