(Updates throughout)

By Mariam Karouny

BAGHDAD, Aug 6 (Reuters) - Shi'ite Prime Minister Nuri al-Maliki's government plunged deeper into crisis on Monday when four ministers loyal to Iraq's first post-war leader Iyad Allawi said they would boycott future cabinet meetings.

A total of 17 ministers in Maliki's cabinet have now quit or are boycotting meetings, at a time when he is under growing pressure from U.S. officials in Washington to make demonstrable progress in reconciling Iraq's warring sects.

There are a total of 37 ministers, including ministers of state, meaning Maliki still has a narrow majority in cabinet.

"We are still in the government but we are boycotting cabinet meetings. We sent a list of demands to Prime Minister Maliki four months ago but he did not respond to it," said Human Rights Minister Wijdan Michael, a member of Allawi's secular Iraqi List.

Infighting has paralysed the government, with no agreement on key laws to distribute oil revenues, allow former members of Saddam Hussein's Baath party back into the civil service and set a date for provincial elections.

Analysts say the political parties are reluctant to compromise, too concerned with protecting their own interests. Sunni Arabs, once dominant under Saddam, say Maliki has marginalised them, fuelling support for an insurgency.

Sunni Arab, Shi'ite and Kurdish political leaders are due to hold a summit soon to try to break the deadlock in what one senior Western diplomat described at the weekend as Iraq's "moment of truth" for chances of a powersharing deal.

The Accordance Front, the biggest Sunni Arab bloc in the national unity government, pulled out its six ministers last week in protest at Maliki's refusal to address a list of demands, including a greater say in security matters.

Six ministers loyal to Shi'ite cleric Moqtada al-Sadr also quit in April to press their demand for Maliki to set a timetable for a U.S. troop withdrawal.

The ministers loyal to Allawi, interim prime minister after the U.S. invasion of Iraq in 2003, are a mix of Sunni Muslim, Shi'ite and Christian and hold the communication, human rights and science and technology portfolios. A fourth is a minister of state.

A fifth Iraqi List minister, Justice Minister Hashem al-Shebly, resigned earlier this year.

Iraqi List lawmaker Iyad Jamal-Adin said the demands included the suspension of a committee charged with rooting out former members of Saddam Hussein's Baath party.

Iraq's minority Sunni community say they have been unfairly targeted in the purge of the civil service.

He said the committee should stop work until the de-Baathification law was passed. The List also wanted Maliki to end what he said was the practice of trying to balance the number of civil servants in ministries according to sect and religion.

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