Averting a potentially serious political crisis, Iraq's National Assembly has voted to reverse a change it made three days ago to rules for the mid-October referendum on the country' draft constitution. The about-face by the assembly follows heavy criticisms by both the United Nations and the United States.

Shi'ite lawmaker Juwad al-Maliki says the assembly found it had to reverse itself, after the United Nations described the rule change as a violation of international standards.

Mr. Maliki says the last thing the Iraqi National Assembly wants during this critical period in Iraqi history is a dispute with the United Nations. But the lawmaker says the assembly's decision to restore the original voting rule should not be interpreted as an admission of any mistakes or guilt.

On Sunday, Shi'ites and Kurdish legislators, who dominate the assembly and largely wrote the constitution, angered Iraq's Sunni Arab minority by creating two different thresholds for passing and defeating the constitution.

For the draft to pass, the assembly said that winning a simple majority of those who cast votes could guarantee it. But for the constitution to be voted down, it would require the much more difficult task of getting two-thirds of registered voters in three provinces to say no.

The existing interim constitution does not specify registered voters. Sunni Arabs, who dominate in at least three provinces, complained bitterly that by raising the bar, Shi'ites and Kurds made it almost impossible for them to try to defeat the constitution. On Tuesday, angry Sunni leaders threatened to call for a boycott of the October 15 referendum.

A majority of Sunni Arabs are against the charter, which endorses a federalist arrangement for Iraq. Sunnis argue that federalism would break apart the country because it gives power and oil wealth to Shi'ites in the south and Kurds in the north and leave little for Sunnis in the middle of the country.

Despite threats by Sunni Muslim extremists, a large number of moderate Sunnis are expected go to the polls to show their disapproval of the constitution.

A Sunni lawmaker, Mishan al-Jabouri, says the only way Sunni Arabs would endorse the charter is if Shi'ite and Kurdish leaders meet at least three Sunni demands.

Mr. Jabouri says the most important demand is that Iraq's oil and other resources be put under central management in Baghdad. The two other demands stipulate that Iraq be declare part of the Arab and Islamic nations, and that a phrase in draft constitution be removed so that it no longer equates Saddam Hussein's Ba'ath Party to a terrorist group.

"If you change the three points, what we asked to change, we will say yes," said Mishan al-Jabouri. "If they do not change, we use our way to say no."

The United States, which has long hoped for a constitution that can help quell the country's Sunni-led insurgency, has been conducting intense behind-the-scenes negotiations with Shi'ite and Kurdish leaders in recent weeks to secure a compromise.

But with just 10 days left before voting day, neither Shi'ite nor Kurdish leaders have yet agreed to any of the changes.