Time is rolling backward in Iraq. The stability achieved in 2007 after the surge of U.S. forces is gone. With bloodshed spreading throughout the country, claiming 7,000 lives so far this year, Iraq appears to be heading once again toward all-out civil war.

Given this violence, and the enormous investment the U.S. has made in Iraq’s future, President Barack Obama has to be forceful with Iraqi Prime Minister Nouri al-Maliki when they meet at the White House tomorrow: More weapons, as Maliki has asked for, will not help end the slaughter. The imperative is for Maliki, a Shiite, to share power with Iraq’s Sunni minority.

Regardless of who is responsible for Iraq’s current predicament -- and Maliki bears most of the blame -- at this point, only Iraq’s prime minister can fix it. To understand why, it’s necessary to go back to the relative calm of 2007, when Sunni leaders, hoping to secure a better political deal with Maliki’s Shiite-dominated government, helped U.S. troops put down the Sunni insurgency. Maliki has not repaid the favor.

The past year of violence was set off by the arrest on terrorism charges of 10 bodyguards of Finance Minister Rafih al-Issawi, a Sunni. Just months before, another Sunni figure, Vice President Tariq al-Hashimi, was sentenced to death in absentia for two murders. To Sunnis, such cases reinforce their belief that Maliki will never meaningfully share power with Iraq’s ethnic minorities.

Mass demonstrations erupted, with protesters demanding an end to sanctions against individuals associated with the former Baathist regime, the release of unjustly detained Sunnis and the reform of Iraq’s Anti-Terrorism Law, which has been exploited to target Sunnis. The law mandates the death penalty not only for those who commit terrorism but also for “all those who enable” such crimes; it defines terrorism so broadly that it could include a peaceful sit-in on a public square.

Against U.S. advice, Iraqi security forces stormed a peaceful Sunni protest camp in the town of Hawijah in April, killing 44 people. That excess invited the return of a worse extreme: bomb attacks by Sunni militants on government sites, Shiite gathering places and Sunnis cooperating with the government. Among the participants is a revitalized al-Qaeda in Iraq, which announced that it had merged with related elements in Syria to form al-Qaeda in Iraq and the Levant.

Syria’s civil war exacerbates the situation, as the sectarian violence there inflames sectarian passions in Iraq. Officially, Iraq is neutral, but it has allowed Iran to fly over its airspace to supply the Syrian regime, which -- like Iraq -- is fighting Sunni insurgents.

In a suspiciously timed op-ed article this week in the New York Times, Maliki pledged to challenge the Iranians if provided sufficient firepower to do so. The U.S. has already agreed to sell the Iraqis an air-defense system, but they also want Apache attack helicopters and accelerated delivery of 36 F-16 fighter planes they have already bought. Maliki wrote that he needs these aircraft to fight “terrorists.” The danger is that the Iraqi government would use them, as has the government in Syria, to hunt its own people from the air.

Maliki needs to understand that he cannot end the mayhem with weapons alone. He knows U.S. forces won’t rush into Iraq again. He may be tempted to reconstitute the vigilante Shiite militias that were responsible for so much killing before 2007, but he has to know that would be a step into the abyss.

Calming the sectarian strife of Iraq will require the collaboration of Sunni leaders. That can only be secured if they have the expectation of gaining a greater share of political power and better treatment of their community. Delivering this message may be the most helpful contribution President Obama can make to President Maliki tomorrow.

To contact the senior editor responsible for Bloomberg View’s editorials: David Shipley at davidshipley@bloomberg.net.