Free and fair elections in Zimbabwe, due at the end of the month, are possible despite a chaotic early vote and concerns from regional powerhouse South Africa, the African Union said Friday.

"According to our observers on the ground we believe that it is possible to have free and fair elections in Zimbabwe. But we cannot guarantee that it will be the most perfect or optimum of situations," said Aisha Abdullahi, AU commissioner for political affairs on Zimbabwe.

The AU announcement comes after South Africa warned there were challenges in the run-up to the vote.

A scheduled early vote by the country's security forces had turned chaotic as thousands of police and soldiers slated to be on duty on election day were unable to vote by the time the two days of polling closed on Monday evening.

Election officials blamed the disruption on problems associated with the printing of ballot papers although the stations had opened late and many lacked indelible ink, stamps, voter rolls and ballot papers and boxes.

"The environment in Zimbabwe so far reassures us that that the conditions are good for the election to be held on July 31," Abdullahi said during a press conference at the agency's headquarters in Addis Ababa.

"The Peace and Security Council has noted the levels of preparation for the election and confirmed that the funding gap has been filled," she said, referring to the panel in charge of enforcing union decisions.

President Robert Mugabe called early polls, hoping to prolong his 33 years in power, despite demands for reform by his archrival Prime Minister Morgan Tsvangirai.

Leaders of regional mediator the Southern African Development Community (SADC) will meet in South Africa on Saturday to discuss the upcoming elections.

The July 31 vote is the first since elections in 2008 which led to the formation of a coalition government between President Mugabe and Prime Minister Tsvangirai but was marred by deadly violence.