WASHINGTON — With a vote on Iraq's draft constitution about a week away, the United States has launched a diplomatic drive to encourage Iraq's Arab neighbors to support the country's fragile political process.

James Jeffrey, the State Department's senior adviser on Iraq, is touring the Middle East, urging Saudi Arabia and other countries to denounce the insurgency, persuade Iraq's Sunni minority to vote in the Oct. 15 referendum and send senior envoys to Baghdad in a show of support.

Washington is hoping participation in the referendum by the disaffected Sunni minority will help create a foundation for political stability in Iraq and for an eventual withdrawal of U.S. troops.

Jeffrey's mission follows one by the U.S. ambassador to Iraq, Zalmay Khalilzad, according to the State Department.

The diplomacy is facing significant obstacles.

Tension between Iraq and its Arab neighbors rose after Saudi Foreign Minister Prince Saud al-Faisal said in Washington two weeks ago that Iraq is "gradually going toward disintegration."

Saud's comments reflect concern in Saudi Arabia — as in most Arab countries, dominated by Sunni Muslims — that the draft constitution would create a weak central state, giving too much power to Iraq's Shiite Muslims and failing to protect Sunnis. Sunnis are the main backers of Iraq's insurgency.

Arab neighbors also worry that a Shiite-dominated Iraq could spark demands for more power from their own Shiite populations.

"I don't think the Sunni Arab neighbors can possibly be very happy about what's going on in Iraq," said Juan Cole, a Middle East expert at the University of Michigan.

Sunni politicians have threatened to boycott the referendum or urge their backers to vote against it.

Saud's remarks and his charges of Iranian interference in Iraq outraged Iraqi Shiite political leaders. They rallied their supporters in Baghdad, telling them they should respond to Saud's comments by supporting the constitution.

Iraqi Interior Minister Bayan Jabr, a Shiite, called Saud "some Bedouin riding a camel" and termed the Saudi monarchy as "tyrants."

Shiite leaders complain that Arab leaders and media haven't denounced Iraq's insurgents or helped rebuild the country politically.