By Pam O'Toole BBC regional analyst

Afghanistan's recent loya jirga or grand assembly was marred by back-room deals and intimidation, says a Brussels based think-tank.

A report by the International Crisis Group (ICG) says the assembly succeeded in according national legitimacy to Afghanistan's peace process and peacefully electing a popular leader - Hamid Karzai - as transitional president.

Former king: Forced to step aside

But, it adds, an all-consuming concern for short-term stability caused key Afghan and international decision makers to bow to undemocratic sectarian demands.

The transitional authority which emerged from the loya jirga, the report warns, will be hampered by its compromises.

Delegates to the loya jirga were under no illusion that this would be a fully democratic process, but nevertheless many were disappointed when it became immediately obvious that many of the decisions would be made outside the tent.

'Delegates intimidated'

The opening of the assembly was delayed as Afghanistan's former king came under pressure from Washington, the United Nations and key Afghan officials to disavow any possible candidacy.

Unelected delegates - including unreconstructed, and unpopular, warlords - were appointed at the last moment.

Delegates were monitored or even intimidated.

Karzai "cannot continue to avoid confrontation"

Even the process of electing Mr Karzai was marred by irregularities and improprieties, including pressure being put on would-be opponents.

Such moves, says the report, stoked fears among many delegates that they were window-dressing for a hidden process, governed by intimidation and power struggles, which allowed no safe space for democratic participation or opposition.

Now Afghanistan's transitional authority faces tremendous challenges, says the report.

Powerful regional warlords have been given places in it and have pledged their loyalty.

But their true willingess to submit to central authority has yet to be tested.

The report concludes that President Karzai must now show strength - he cannot continue to avoid all confrontations with commanders around the country and in his own government.