US hits stumbling block in attempts to build interim government involving Ahmed Chalabi

America is struggling to put together a meeting of "free Iraqis" next week – a delicate venture that has been made even trickier by the killing yesterday of two leading clerics in a bloody incident at one of Shia Islam's holiest shrines.

The talks, expected to be held at an air base near the southern city of Nasiriyah, will be the first step towards the creation of an interim authority for post-Saddam Iraq. This will see Iraqis working alongside US supervisors, in the transition phase before a new permanent system of government is installed.

The meeting will embrace internal figures who are untainted by involvement with the previous regime, and representatives of exiled opposition groups – among them Ahmed Chalabi, the leader of the Iraqi National Congress (INC).

But matters have been greatly complicated by the deaths of the two clerics – Sayyed Abdel Majid al-Khoei, just arrived from exile in London and sympathetic to the US-led invasion, and Haider al-Kadar, appointed by Saddam Hussein's Ministry of Religion – at the hands of a mob at the shrine of the Imam Ali, in the city of Najaf.

The incident symbolises the immense difficulties America faces in its search for a temporary government acceptable to the various ethnic and religious groups in the country.

Invitations to the meeting have been sent out by General Tommy Franks, head of US Central Command, to about 40 Iraqis inside the country as well as the six main exile groups. The internal figures have been selected by the CIA.

America was starting to "identify who in a community are the leaders and who have been leaders for long, long periods of time", Colin Powell, the Secretary of State, told the Los Angeles Times. "Who do people look to? They look to tribal leaders. They look to religious leaders. You start to build on that." But as the killings in Najaf showed, even those religious leaders can be divisive, rather than unifying, elements.

A priority next week will be to overcome mutual distrust and rivalry between opponents of Saddam Hussein who stuck it out inside Iraq, and the exiles – some of them suspected of riding in on the back of the Allies, back to a country that they hardly know.

Such misgivings are especially directed at Mr Chalabi, a divisive figure even in Washington. Favoured by the Pentagon but deeply distrusted by the State Department and the CIA, Mr Chalabi was ferried from a temporary base in northern Iraq to Nasiriyah last week by the US military.

But the White House has quietly moved to thwart a meeting of exile groups that Mr Chalabi intended to convene today or tomorrow – widely seen as a pre-emptive strike of his own to ensure a dominant INC role in the transition. For public consumption, the Bush administration insists it has no favourites, and that Iraqis themselves must choose their own representatives.