Zambia's three main opposition parties have formed an alliance to oppose current President Levy Mwanawasa in elections later this year.

The new United Democratic Alliance said Wednesday that it will select a single presidential candidate at a joint convention.

The new alliance is made up of three parties: the United Party for National Development, Forum for Democracy and Development, and United National Independence Party.

Some political experts see the new umbrella party as a significant threat to President Mwanawasa, who is seeking a second term.

No date has been set yet for Zambia's presidential, parliamentary and local government elections.

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