Bolivia's president has set out plans for radical reforms in an attempt to end weeks of violent protests which have partly paralysed the nation.
Key roads have been blocked during the protests
Carlos Mesa said the constitution would be rewritten by a new assembly that would be elected on 16 October.
He said a referendum on the same day would decide on a demand for more autonomy by resource-rich provinces.
The move should satisfy both sides of Bolivia's regional and ideological divide, a BBC correspondent says.
Trades unions and indigenous groups have been calling for the nationalisation of Bolivian gas.
Provinces of Pando, El Beni, Santa Cruz and Tarija seeking more autonomy
They hold most of Bolivia's gas and oil resources
Indigenous Aymara and Quechua peoples make up around 60% of population
Many live in poor Andean highlands
Form majority in La Paz
Protesters backing the demand have blockaded large areas, and the main city of La Paz has been cut off from the rest of the country.
They say a law which increases taxes on foreign gas investors does not exert enough control over the country's resources.
President Mesa has said the gas law is too punishing for the multinationals that have invested billions of dollars in Bolivia's gas fields.
BBC South America correspondent Elliott Gotkine says the president is unlikely to agree to the protesters' demand for nationalisation.
Demonstrators have also been calling for constitutional reform to give more power to the indigenous majority, who are mainly from the impoverished highlands.
The protesters also want to stop the congress from granting autonomy to the wealthier provinces in the east and south.
Mr Mesa's announcement of reform plans follows three days of deadlock in congress.
Members postponed their parliamentary session and said they would not meet again until Tuesday.
In a televised announcement, Mr Mesa said Bolivia "cannot wait".
"The country is experiencing a very critical moment, a high risk confrontational situation," he said.
"[Bolivia] is being subjected to pressure that could make it explode," he added.
The president called on the Catholic Church to act as a mediator between politicians and social leaders.
A similar dispute led to the overthrowing of Mr Mesa's predecessor, Gonzalo Sanchez de Lozada, in October 2003.
The president has vowed to remain in office for his full term, despite frequent political crises.
He is backed by the armed forces, which last week sacked two officers after they claimed to represent a new nationalist movement in the military.