A vote to choose a new chairman for the African Union's (AU) influential executive commission has ended in deadlock, with a new election will be held in June, Michael Sata, Zambia's president, has said.

The deadlock at the summit in Addis Ababa comes as a surprise because of the intense campaigning ahead of the vote, almost overshadowing the two-day summit on intra-African trade.

"We went for an election and none of the two candidates emerged as a winner," Sata told journalists on Monday, referring to Nkosazana Dlamini-Zuma, South Africa's home affairs minister, who sought to unseat Jean Ping, the current chairman, from Gabon.

South Africa has lobbied hard to see Dlamini-Zuma unseat the Gabonese career diplomat who has been in the job since 2008.

However, Ping narrowly edged ahead of Dlamini-Zuma in the first three rounds of voting, AU sources said, but was short of the two-thirds majority needed for an outright win.

Al Jazeera's Nazanine Moshiri, reporting from the summit, said there was speculation that there had been negotiations between Dlamini-Zuma and Ping for one of them to stand aside.

Erastus Mwencha, the Kenyan deputy AU commission chief, will serve as the executive council's chair until a fresh poll, which Sata said would take place in June, during the next AU summit in Malawi.

South African delegates broke out into song and dance after the vote, held in the new ultra-modern Chinese-donated AU headquarters which were unveiled at the weekend.

The summit is expected to conclude a deal on bolstering trade between African nations, which currently trade more with the West and China than with themselves.

On Sunday, the 54-member organisation elected Benin's President Thomas Boni Yayi as their new chairman, a rotating post held for one year.