Talks aimed at ending Zimbabwe's political crisis appear to be deadlocked.

Zimbabwe opposition leader Morgan Tsvangirai addresses the media in Harare, 02 Jul 2008

Officials close to the talks say the sides are at an impasse over what position Morgan Tsvangirai, leader of the opposition Movement for Democratic Change, would hold in any unity government.

The MDC says negotiators for the ruling ZANU-PF party have offered Tsvangirai a third vice presidency with no executive power.

Tsvangirai is said to be heading to the site of the talks in Pretoria, South Africa to consult with his negotiators.

The information comes from anonymous sources close to the talks, since both sides agreed on a media blackout.

President Robert Mugabe (file photo)

Tsvangirai has insisted he lead any unity government because he won the first round of voting in March. President Robert Mugabe was declared the winner of a June run-off many observers dismissed as a sham.

The opposition leader pulled out of the run-off, due to what he described as widespread state-sponsored violence aimed at his supporters.

ZANU-PF and the MDC began talks on a power-sharing government last Thursday.

The agreement leading to the talks called for an end to all violence. But human rights monitors say three known MDC supporters have been killed in the last week.

Some information for this report was provided by AFP, AP and Reuters.