BAGHDAD, Iraq, Oct. 26 - Leaders of three Sunni political parties joined together Wednesday to compete in the Dec. 15 parliamentary elections, a sign that the country's embittered Sunni Arab minority might play a more active role in the democratic process.

The alliance, the Iraqi Concord Front, will field candidates in the elections for a new National Assembly and work as a bloc to advance Sunni interests, said leaders of the three groups involved: the Iraqi Islamic Party, the National Dialogue Council and the Iraqi People's Gathering.

The leaders' statements suggested that they harbored large ambitions, including the leadership of all of Iraq's estimated five million Sunni Arabs.

Alla Makki, a leader in the Iraqi Islamic Party, said the alliance would field some 230 candidates. The alliance's leaders also said they would try to persuade guerrillas to lay down their arms, and would press the Americans to withdraw their troops.

The announcement came a day after Iraqi election officials announced that the country's new constitution had been approved by a large majority of voters. The charter failed in the three provinces where Sunni Arabs are a majority; it is those same provinces where the guerrilla insurgency churns strongest.

The rejection of the charter by Sunni Arabs, coupled with their widespread boycott of the elections in January, gave rise to doubts about whether the Sunnis would field candidates and vote in the December elections. The elections in December are critical in shaping Iraq's political future: the National Assembly to be chosen is to sit for four years, and it will be empowered to amend the constitution.

The elections are also a cornerstone of the Iraqi-American strategy to co-opt the insurgency by encouraging Sunni Arabs to take part in the democratic process along with the Kurds, most of whom are also Sunnis, and the Shiites. So far, that process has shown few signs of success.

The unveiling of the Iraqi Concord Front on Wednesday suggested that at least some Sunni leaders, even some who opposed the constitution, might be willing to give the process a try. Two of the three parties in the coalition opposed the constitution. The Iraqi Islamic Party was the only major Sunni Arab group to support it.

Mahmoud al-Mashahadani of the National Dialogue Council said, "We will have our unified Arab Sunni bloc, and we will not allow any other Arab Sunni to negotiate with the Kurds or the Shiites."

He added: "If we succeed, then we will be able to persuade the resisters to use the political solution.

"We will tell the resisters: "Come and talk with us - we could represent you. We are Arab Sunni; we can be the best mediator.' "

The chain of events described by Mr. Mashahadani is one of the principal goals of the Iraqi government and American officials here: to use the democratic process to draw Iraqis away from supporting the insurgency.

But Mr. Mashahadani's statements raised another possibility much discussed here: that the Sunni Arab members of Parliament would become a kind of political wing of the insurgency, much the way that Sinn Fein was in the British Parliament for the Irish Republican Army.

Still, some prominent Sunni leaders refused to join the alliance, among them members of the National Dialogue Council. Some of them said they were planning on forming their own coalition.

One was Saleh Mutlaq, who became the most vocal Sunni opponent of the constitution this summer. Mr. Mutlaq, a member of the National Dialogue Council, said he intended to join another coalition that included Iraqi leaders of all ethnicities and sects.

But Mr. Mutlaq said his biggest concern was whether the Sunni Arabs would vote in December. He said he believed that the Sunnis would have succeeded in defeating the constitution with a two-thirds "no" vote in three provinces were it not for widespread fraud in two of them, Nineveh and Diyala.

"We are not sure if they will vote" in December, Mr. Mutlaq said. "The lesson was very bad. This is what worries us."

Some prominent voices emerged Wednesday to denounce the constitution, if not the elections to come. At a news conference in Baghdad, Abdul Salam al-Kubaisy, a leader of the Association of Muslim Scholars, said the constitution was part of an American conspiracy to "shred this country into pieces."

The association represents hundreds of Sunni mosques around Iraq.

Mr. Kubaisy, speaking at the Umm al Qura Mosque, acknowledged that many Sunnis had gone to the polls, but he accused the Americans of fraudulently turning Sunni no votes into yes votes.

"The noes have been changed just to approve the American conspiracy to steal the history and the past and the present of Iraq," Mr. Kubaisy said. "This constitution will be terminated when they leave."