By Ian McWilliam BBC Kabul correspondent

President Karzai hopes the reforms will help strengthen security

The reforms, aimed at creating a more equitable ethnic balance in the ministry, should open the way for a nationwide disarmament programme.

A spokesman for President Hamid Karzai said that new defence ministry appointments should be made within the next two weeks.

The spokesman said that 22 new appointments should be made within the coming weeks. The Defence Minister, Marshal Fahim, will retain his post.

Ethnic divide

The disarmament programme is expected to go ahead once the reforms have taken place.

US troops have been hunting down Taleban fighters

Many commanders would be unwilling to surrender their weapons to a ministry run by a single faction.

The key ministries have been dominated by an ethnic Tajik faction since the collapse of the Taleban.

But historically Afghanistan has been ruled by its largest ethnic group, the Pashtuns.

Pashtun complaints that they have too little representation in the corridors of power have contributed to the government's instability.

Government offensive

Crucially, they have also fed support for a violent Taleban insurgency in the southeast of the country.

For the past week, American troops have been backing up an Afghan Government offensive against a large group of fighters in Zabul province.

A US spokesman said American forces began a news offensive in Zabul on Saturday with aerial attacks on Taleban bases in the mountains there.