Zimbabwe Prime Minister Morgan Tsvangirai on Sunday accused President Robert Mugabe of violating their power-sharing deal, as thousands rallied to mark his party's 10th anniversary.
Despite guarantees of political freedoms in the unity accord, Mugabe's Zanu-PF party continues to persecute supporters of his Movement for Democratic Change (MDC), Tsvangirai said.
"I am not going to stand by while Zanu-PF continues to violate the law, persecutes our members of parliament, spreads the language of hate, invades our productive farms (and) ignores our international treaties," he said.
"I am not going to stand by and let this happen," he said, to cheers from the crowd that included dancers in feathered masks, traditional drummers and families with children sprawled on the grass under the summer sun.
"We want partners that are sincere... We want partners who are going to commit themselves to good governance principles," he said. "We cannot have partners of looters."
Tsvangirai joined Mugabe in a unity government in February in a bid to end political unrest that erupted after last year's failed elections. But the two remain deadlocked over key appointments, while Mugabe stands accused of dragging his feet over reforming media laws and the security forces.
While MDC supporters rallied in the second city of Bulawayo, an EU delegation in Harare wrapped up a two-day visit to Zimbabwe, the first in seven years, calling for greater protection of human rights.
"We still have a lot of reports on human rights violations. That is unacceptable and not the spirit" of the power-sharing deal, said Swedish Development Minister Gunilla Carlsson, whose country holds the rotating EU presidency.
Despite tensions within the government, life for most Zimbabweans has improved this year, after the local currency was abandoned following years of hyperinflation.
Shops across the country closed their doors last year, unable to replenish stocks, while crops failed across the country, leaving nearly seven million people in need of food aid ? more than half the country.
This year, the UN estimates less than three million people will need food aid, while businesses are slowly resuming operations, though most of the population remains deeply impoverished.
"We are now free. We can work, we can eat. Now we can eat bread," said Gladys Sengwayo (44) who brought her infant granddaughter and three other family members to the rally.
EU aid commissioner Karel de Gucht said positive reforms in Zimbabwe would lead to more aid.
"If there is positive response, we can do more. We are presently in the European Commission working on a package and we hope to finalise it by the end of this month," he said.
"But it's also very much in the hands of the Zimbabweans. The more they give us the possibility to do, the more we will do but the conditions have to be met."
The MDC was formed on 11 September 1999 after a coalition of rights groups, churches and civic society agreed to launch an opposition party to challenge Mugabe's rule.
The party made rapid electoral gains in its first year, finally seizing a parliamentary majority in last year's elections, when Tsvangirai also defeated Mugabe in a first-round presidential vote his supporters that MDC says left more than 200 dead. Former South African president Thabo Mbeki mediated a unity accord one year ago that eventually led to the power-sharing government.
The unity government is meant as a transitional authority to oversee the writing of a new constitution that will guide the nation to fresh elections.
Tsvangirai has launched a major effort at normalising ties with western nations, who have imposed sanctions on Mugabe and his inner circle following 2002 elections that western observers and local poll monitors said were flawed.
Mugabe regularly lashes out over the sanctions, which include a travel ban and asset freeze on his family and top aides.