In the Democratic Republic of Congo, former rebels backed by the Ugandan government threatened late Wednesday to pull out of the country's fragile transitional government. The threats came as South Africa's president, Thabo Mbeki, spent the day in Kinshasa speaking with Congo's political leaders to seek a breakthrough in the stalling peace process.

Thabo Mbeki, South Africa's president and one of the continent's leading peacemakers, arrived in Kinshasa Wednesday to help find a breakthrough in the Democratic Republic of Congo's stalled peace process.

But although the South African leader gave an upbeat assessment of his lengthy meeting with President Joseph Kabila and the Congo's four vice presidents, little progress seems to have been made in resolving yet another crisis blocking the organization of elections in June.

Just minutes after meeting with the South African president, Jean-Pierre Bemba, head of the former Ugandan-backed Movement for the Liberation of Congo rebel group, threatened to pull out of the government unless substantial progress was made by the end of the month.

Mr. Bemba accused those around President Kabila of blocking and delaying the application of the power-sharing deals that were put in place in 2003 and ended a five-year war that sucked in six neighboring countries and killed over three million people.

The former rebel leader said his complaints went beyond the recent sacking of one of his ministers who was accused of corruption. He called for the reforms of the security forces, local administration and public enterprises, reforms that had already been agreed upon but not yet implemented.

He warned that, as matters stand, elections could not be held in June, and said his party did not want to be held responsible for any delay.

Political tension has risen in the past few days after the head of the electoral commission suggested the polls were likely to be postponed, sparking violent riots in Kinshasa.

After the talks Wednesday, Mr. Bemba said he would return to his northern base of Gemena.

His critics in President Kabila's camp accused him of blocking the peace process. And Vice-President Abdoulaye Yerodia told reporters that Mr. Bemba and his supporters represented little more than a return to Mobutism, a reference to the more than 30 years of corrupt regime of the late Mobutu Sese Seko.

But independent analysts say the deterioration of the political climate in the Congo can largely be blamed on President Kabila's inability to control the various factions comprising the transitional government. They say the 34-year-old president portrays an image of weakness by calling on the South African president every time there is a serious crisis.