A prominent Democratic lawmaker has renewed his call to keep Iraq together by giving greater autonomy to Shiites, Sunnis and Kurds.

Sen. Joseph Biden also criticized the administration of President Bush for having no coherent strategy for success in Iraq, other than preventing a U.S. defeat and turning the problem over to its successors in 2009.

Biden, a potential presidential contender in 2008, is the top Democrat on the Senate Foreign Relations Committee. He has often traveled to Iraq.

He first made his proposal on Iraq four months ago along with Leslie Gelb, president emeritus of the Council on Foreign Relations.

Writing in The Washington Post, Biden said, "The new central reality in Iraq is that violence between Shiites and Sunnis has surpassed the insurgency and the foreign terrorists as the main security threat."

He said massive unemployment feeds the ranks of sectarian militias and criminal gangs.

"No amount of troops can solve this problem," he said. "The only way to hold Iraq together and create the conditions for our armed forces to responsibly withdraw is to give Shiites, Sunnis and Kurds incentives to pursue their interests peacefully and to forge a sustainable political settlement."

To maintain a unified Iraq, Biden proposed decentralizing it and giving Shiites, Sunnis and Kurds their own regions as was done when Bosnia was divided into ethnic federations. The central government would be left in charge of common interests such as border security and the distribution of oil revenue.

The plan "would bind the Sunnis to the deal by guaranteeing them a proportionate share of oil revenue," Biden said. "Each group would have an incentive to maximize oil production, making oil the glue that binds the country together."

He said the plan was consistent with Iraq's constitution, which already provides for the country's 18 provinces to join together in regions, with their own security forces and control over day-to-day issues.

Baghdad, the capital, would be maintained as a federal city, belonging to no one region. "This plan is the only idea on the table for dealing with the militias, which are likely to retreat to their respective regions instead of engaging in acts of violence."

Biden said it is not partition — "in fact it may be the only way to prevent violent partition and preserve a unified Iraq."

He challenged those who reject his plan to come up with an alternative.

When he first presented his ideas four months ago, critics wondered how a weak central goverment in Baghdad could prevent sectarian fighting, protect women and minorities, ensure even distribution of oil wealth and avoid regional interference in Iraqi affairs.