"He met with Ban Ki-moon for half an hour," the official, who asked not to be named, told Reuters at the U.N. Conference on Trade and Development (UNCTAD) in Ghana's capital, Accra.

Zimbabwe's opposition says Tsvangirai won March 29 presidential polls and that President Robert Mugabe, who has ruled since independence in 1980, is attempting to cling to power by delaying declaring the results.

African leaders have come under international pressure to take strong action to help resolve the crisis in Zimbabwe, a once prosperous nation whose economy is in ruins, beset with 165,000 percent inflation and mass unemployment.

Former colonial power Britain on Monday accused Mugabe of trying to steal the election and urged African leaders to do more to help resolve the dispute, saying democratic legitimacy throughout the continent was at stake.