Iraqi Kurdish President Masoud Barzani salutes the crowd while attending a Sept. 16 rally in Dahuk, Iraq, to show support for a Sept. 25 independence referendum. (Ari Jalal/Reuters)

Iraqi Kurds are set to vote next week on independence from Iraq in what many say is a popular expression of their desire for self-determination after suffering for a century under war and dictatorship.

But their staunchest ally, the United States, opposes the move, as do Iraqi rivals and regional powers. They say it could spark new conflicts and aggravate old ones at a time when the nation is on the cusp of defeating the Islamic State.

Kurdish officials pushing the Sept. 25 referendum say there is no need to panic. The poll, which is widely expected to result in a resounding vote to secede from Iraq, is simply an important first step in what would be a lengthy but amicable divorce from the Iraqi state, they say.

“We will ourselves not initiate a clash or a fight,” said Rowsch Shaways, a former deputy prime minister of Iraq and the head of the Kurdish delegation negotiating with Baghdad. “We are pledging dialogue and a peaceful solution.”

Still, the lead-up to next week’s vote has already resulted in political fallout and threats of violence, and the United States has shown little ability to persuade the Kurds to delay the referendum in favor of continued negotiations with Baghdad over disputed territories and revenue-sharing.

Iraqi Kurds take part in an event in Irbil on Sept. 16 to urge people to vote in the independence referendum. (Safin Hamed/Agence France-Presse/Getty Images)

Neighbors Turkey and Iran, concerned over calls for independence by their own sizable Kurdish populations, have threatened to close borders and cancel trade and security agreements with Iraqi Kurdistan.

Anxiety over the referendum was most evident in Kirkuk, a province in central Iraq that has vast oil reserves and is populated by a mix of Kurds, Arabs and Turkmens. Over several decades, it has been the center of demographic manipulation projects based on the ethnicity of whoever hoped to rule it.

Violence flared in the provincial capital, also called Kirkuk, on Monday night when gunfire outside the headquarters of a local Turkmen party left two Kurds dead, prompting Kurdish riot police to descend on the scene. Najat Hussein, an official with the provincial government, said several ­vehicles and motorcycles drove by the headquarters and opened fire. Guards at the party office shot back, killing two of the alleged attackers, he said.

Hussein said it was not immediately clear whether the violence was related to the referendum. “We hope it won’t be the spark that will be the beginning of a fire that will inflame the whole city,” he said.

Police imposed a curfew following the fatal shooting and other smaller skirmishes that broke out between Kurds and Turkmens, local officials said. In one instance, people torched a police car.

Kirkuk has been claimed by both Arabs and Kurds for decades, and a U.S.-brokered process after the 2003 invasion to determine the city’s disposition has gone nowhere.

It is legally under the authority of the central government but has been governed by Kurds since 2014, when Kurdish peshmerga fighters took Kirkuk as the Iraqi military buckled and retreated under the threat of an Islamic State assault.

Turkish tanks are seen near the Habur crossing between Turkey and Iraq during a military drill on Sept. 18, 2017, a week before Iraq's Kurdish region holds an independence referendum. (AFP/Getty Images/AFP/Getty Images)

Since then, the semiautonomous Kurdistan Regional Government, which the United States helped create in northern Iraq after 1991, has asserted its power, exporting oil independently and patrolling its prosperous streets.

Iraq's parliament last week voted to oust the Kirkuk provincial governor, a Kurdish physician with dual U.S. citizenship, over his support for the referendum. He has refused to step down. For months before that, he and his Arab deputy governor stopped talking because of differences over the independence vote.

Streets here are bereft of the green, orange and white Kurdish regional government flags and banners urging participation that have lined boulevards in other Kurdish cities.

Entreaties to vote “yes” are more subtle, and the loud campaign for high turnout that has produced massive rallies in the Kurdistan capital, Irbil, has been replaced with quieter debates among neighbors and friends who hope the referendum will not disturb their fragile coexistence.

“I have lots of Kurdish friends, and there are no tensions,” said Ahmed Waleed, a 31-year-old Arab who owns a men’s clothing shop. “No one knows if this will continue after the referendum.”

The United Nations has opposed the referendum, saying it threatens Iraq's unity. No international observers will participate in monitoring the vote, raising questions about its credibility.

Rakan Saeed al-Jobouri, the Arab deputy governor of Kirkuk, said Arabs there have come to him with fears of forced displacements by Kurdish security forces under the rubric of fighting terrorism. Human Rights Watch said this has already happened since late last year.

“Legally, constitutionally and practically, [the referendum] is totally compromised,” he said.

Jobouri said that if independence is approved, he and other Arab officials in the city will ask Baghdad for federal protection — which raises the specter of Iraq’s military entering the city to assert control and potentially sparking armed conflict with peshmerga forces already in Kirkuk.

In an interview with the Associated Press, Iraqi Prime Minister Haider al-Abadi, who opposes the referendum, said he would deploy Iraq's military to restore order if unrest breaks out in response to the vote. On Monday, Iraq's Supreme Court ordered the suspension of the referendum after Abadi argued that it is unconstitutional. But Kurdish officials did not budge.

Kirkuk has also been the focal point of internal Kurdish disagreements about the prospect of an independent state. It is controlled by a political party whose members have questioned the intentions of Kurdistan President Masoud Barzani’s party.

Kurdish critics of Barzani say he is using the vote to solidify his power and legacy at a time when his authority is weak because of a financial crisis. Declining oil prices have stalled the economy, and civil servants and peshmerga fighters have not received full salaries for years. The regional government is billions of dollars in debt, and its deputy prime minister said the economic decline is a greater threat to Kurds than the Islamic State.

Enthusiasm for the referendum has also been tepid in Sulaymaniyah, one of the three large provinces that make up the Kurdistan region.

Analysts say Barzani is overreaching by including Kirkuk in the referendum. If the vote for independence there comes back “no,” or if “yes” fails to win by a large margin, Baghdad could use the results for leverage to scuttle the overall project for Kurdish independence. “Holding a referendum there without concern for Arab and Turkmen interests could result in the refusal of independence and resorting to violence,” said Kamal Chomani, a Kurdish analyst with the Tahrir Institute for Middle East Peace, who opposes the referendum.

Kirkuk’s status has implications beyond Iraq’s borders and could ignite a wider regional conflict.

Turkish President Recep Tayyip Erdogan has chided Barzani — a longtime ally — for “political inexperience” in pressing ahead with the referendum. Erdogan has repeatedly described the territorial integrity of neighboring Iraq as sacrosanct and a matter of national security for his country.

Opposition leaders have pressed Erdogan to take a harder line on the vote, citing Turkey’s deep ties to Turkmens in Iraq, especially in Kirkuk.

The Turkish army said Monday that it has launched military exercises on the border with Iraqi Kurdistan, according to local Turkish news reports.

The United States has used the rhetoric of fighting terrorism to encourage Barzani to postpone the referendum, but the episode has illustrated a rare instance of U.S. impotence in swaying Kurdish leaders. After months of failed talks, the White House issued a blunt statement last week urging the Kurdish government to call off the vote, which it described as "provocative and destabilizing."

A U.S. official involved in negotiations with the Kurds, who requested anonymity to discuss sensitive talks, said that the Trump administration has not threatened to withhold the Defense Department’s $22 million fund for the peshmerga but that it could be used as a “lever of influence.”

Defunding the peshmerga, however, would damage U.S. interests in Iraq, where it is heavily involved in the fight against the Islamic State, the official said. Instead, diplomats have urged the Kurds to consider Iraq’s unpredictable politics.

They have argued that Abadi, a pro-U.S. prime minister who has pushed back against Iranian influence, is the best partner the Kurds have to secure their interests. Holding the referendum could empower more-sectarian political forces and bring them to power in Iraqi elections next year, the official said.

Kurdish officials leading the referendum effort acknowledge that it will not lead to a sovereign state soon. Instead, they say it is a democratic exercise that strengthens their hand with Baghdad in ongoing talks over a future independent state and its borders, said Shaways, the Kurdish negotiator.

For their part, Kurds eager for their own country said they are willing to endure any hardships resulting from the vote.

“Being part of Iraq has never brought us peace and never will,” said Saman Xoshnaw, 46, a grocery shop owner. “We are ready to face any difficulties as a result of our decision. We have to sacrifice to get freedom.”

Aaso Ameen Schwan in Irbil and Kareem Fahim in Istanbul contributed to this report.