By Catherine Davis BBC correspondent in Kabul

Mr Karzai is struggling to impose his rule beyond Kabul

The body, which replaces a smaller drafting commission, will start a process of public consultation, culminating in a constitutional loya jirga, or grand council.

The final text is due to be published at the end of October as set out in the Bonn agreement.

The deputy head of the United Nations in Afghanistan called the commission's appointment a monumental step forward and a necessary milestone for moving ahead.

Warlords

The aim has been to make the commission as representative as possible.

The country has suffered years of war

There is much riding on this constitutional process and it is important that ordinary Afghans feel that they have a voice.

Teams will be working throughout the country to inform and consult the public.

Few, though, underestimate the challenge ahead.

There is already concern about possible intimidation, and whether people will feel free and be able to express their views.

Local and regional commanders remain powerful figures. The government's power outside Kabul is tenuous.

Stability

Key issues have to be resolved in the coming months.

One is what role Islam will play in the constitution. Political developments will also have an impact.

If disarmament, for example, goes ahead successfully, many Afghans are likely to be more interested in, and positive about, the constitutional process.

Government officials and the international community have emphasised the importance of this new constitution for unity and stability in Afghanistan.