Seven of Nepal's opposition parties have said they will unite to fight for the restoration of democracy.
The parties will pursue a peaceful nationwide protest, says Koirala
They demanded King Gyanendra give up the direct power he assumed in February and reinstate the parliament he dissolved three years ago.
They also demanded the release of all detained activists and the restoration of suspended civil liberties.
The king has said he assumed power because political parties had failed to tackle the country's Maoist insurgency.
The decision to form a united front has come amid criticism that the opposition parties have not had a common strategy to deal with the country's current difficulties.
The parties said they would launch a peaceful movement across the country to press their demands.
They said a reinstated parliament would create an all-party government and the environment for holding peaceful negotiations with the Maoist insurgents.
President of the Nepali Congress party and former prime minister Girija Prasad Koirala said he did not see any possibility of a dialogue with the monarch at the moment.
He said India, the United States and the United Kingdom must not resume military assistance to Nepal unless the king restored civil liberties.
Mr Koirala also said the seven opposition parties would announce their programme on their nationwide agitation within a few days.
Analysts say the united approach could increase pressure on King Gyanendra who is already facing great international criticism.
King Gyanendra says he is committed in the long term to a multi-party democracy and constitutional monarchy.