Charles A. Duelfer led the Iraq Survey Group, created to search for weapons of mass destruction after the 2003 invasion. Samir S. Sumaidaie was Iraq’s ambassador to the United States from 2006 to 2011.

Iraq has imploded. The extremists from the group that recently renamed itself the Islamic State represent a mortal threat to the country and the broader region, and neither Baghdad nor Washington can remove this malignancy by military means alone. It can be excised only in concert with local Sunni populations that now either harbor the Islamic State or tolerate it because it is seen, misguidedly, as a means of salvation from a loathsome, oppressive central government.

Sunnis do not seek to rule Iraq, but they will no longer tolerate discrimination. Since coming to power, Iraqi Prime Minister Nouri al-Maliki has treated elections under the newborn Iraqi democratic system as a ­winner-take-all proposition — leaving the Sunni population increasingly convinced that it stands to lose all.

Maliki and his cronies have politicized key institutions, including the army, which has collapsed under the leadership of corrupt, unqualified officers as the Islamic State’s fighters have advanced. Pouring resources into such a force without reform will not produce good results. Therefore, to defeat this threat, it is essential to give Sunni communities a stake in a new, cleaner and more just national government that does not treat them as second-class citizens. The policy of the United States must have this truth as its foundation.

There are key points about Iraq that may not be apparent to decision-makers in Washington.

Shiite Muslim volunteers from the Iraqi Ketaeb (brigade) Hezbollah, march as they join the Iraqi army to fight against jihadist militants of the Islamic State. (Ahmad Al-Rubaye/AFP/Getty Images)

●Most Iraqis still identify themselves as Iraqis first and foremost; the use of sectarianism as a political tool has created polarization not previously seen in Iraq, but this is reversible.

●Although there is residual concern in Iraq that many Sunnis, especially former Iraqi army and Baath Party members, seek a return to authoritarian rule by a Sunni strongman (Saddam Hussein redux), this is a myth that suits Maliki. The large majority of Baath Party members in the old regime were simply professionals or military men who participated in the party because it was the only way to pursue their careers. And for all of the horrors of Saddam’s leadership, the Baath were steadfastly secular. They are natural foes of the Islamic State, not allies. Recent reports of the Islamic State killing senior former Sunni military leaders is evidence that it recognizes this vulnerability.

●It is likewise a myth, in this case propagated by Sunni extremists, that most Iraqi Shiites are loyal to Iran. Thousands of Iraqi Shiites died fighting in the Iraq-Iran war in the 1980s. The Shiites in Iraq are mostly Arab, and Iranians are mostly Persian. Like people everywhere, Iraqis’ identities are multifaceted; only a portion have sectarian affiliations.

People continue to talk of a “national unity government” as a solution to the grave problems facing Iraq, but this approach has already failed. For 10 years, Iraq has had governments formed with quotas of ministers from different communities. But ministers not from Islamist Shiite parties were undermined by the flooding of their departments with appointees from “approved parties.” Such ministers became hood ornaments. The same applies in the armed forces, universities, the media and other nominally independent institutions that were brought under the prime minister’s control.

What is needed, instead, is a “government of national salvation,” headed by a prime minister acceptable to all communities and girded by checks and balances to ensure that the new political order will be free from discrimination. Such a government must represent genuine, substantive change away from sectarianism. The current political order cannot reform itself; new professional talent must be brought in from outside it.

But it seems that Iran is having none of that. Reports from inside the government indicate that Iran has vetoed all Shiite nominees to the prime minister’s post who are remotely acceptable to Sunnis or secular Shiites. That means the crisis will continue and a fire that could otherwise be extinguished by an Iraqi political solution will spread.

The question now is whether the United States has the will to do what is necessary to allow Iraqis to freely arrive at a political solution and prevent Iran from blocking it.

Left to their own devices, Iraqis would have a chance of solving their problems and rolling back the Islamic State. But they do not. Everyone in the region wants to influence events, but only Iran has gone so far as to block the compromise that is needed to bring Sunnis into the tent. Iran’s stranglehold on Baghdad’s political process must be broken. If it is not, a big chunk of a fragmented Iraq, with vast reserves of oil, could turn into a vassal state of Iran — following a civil war, with all of its misery and devastation.

Washington needs to cut off Maliki. Period. To counter Iran, it also needs to assign a respected and experienced American representative who has real authority and is empowered to achieve the essential goal of defeating the Islamic State. This representative — acting in a role similar to the one that the late Richard Holbrooke played in Afghanistan and Pakistan in 2009 and 2010 — needs to meet with opinion leaders in the Shiite and, especially, Sunni communities. Sunnis must be convinced by action and deed that Washington will not abandon the principle of inclusion. The envoy needs to make deals and deliver.

The situation in Iraq is very bad but still solvable. The Islamic State is the present danger, but it is a symptom of the root problem: A sectarian clique has subverted a nascent democratic system for its own benefit. Because of this, the local Sunni populations, who have no predisposition for anything the Islamic State represents, do not yet have sufficient incentive to eliminate it. That must be changed.