The new assembly will write a constitution, a key demand of former Maoist rebels.
Unrest in Tibet has revealed a generational fault line that is likely to sharpen as Olympics near.
Tibetans have protested in both countries, which have long accepted Tibetan refugees but restricted their political activities.
Exiles in India vowed to defy a police ban on their march to Tibet, launched Monday.
National elections – already twice delayed – are scheduled for April. The interim government voted to abolish the monarchy, meeting a key demand of former Maoist rebels.