Zimbabwe's ruling and opposition parties make no progress toward breaking a political impasse in talks Monday, but agree to meet again later in the week.

The talks, sponsored by Nigeria and South Africa, are the first face-to-face meeting between the rival groups since last month's disputed presidential election.

The leader of the opposition delegation (Welshman Ncube) repeated his party's call for a new vote, saying there is no other way to go forward.

Speaking for the government, Justice Minister Patrick Chinamasa rejected the demand, saying the results of the election are non-reversible and non-negotiable.

Robert Mugabe was re-elected president last month over challenger Morgan Tsvangirai of the Movement for Democratic Change. Independent observers say the vote was deeply flawed and the Commonwealth suspended Zimbabwe from the union for conducting a poll it declared neither free nor fair.

Even though both sides remain intransigent, the government and some foreign diplomats expressed optimism that the talks were held at all, and that they will continue Wednesday.