By David Ignatius

The Manchester terror attack by an alleged Islamic State “soldier” will accelerate the push by the U.S. and its allies to capture the terror group’s strongholds in Mosul and Raqqah. But it should also focus some urgent discussions about a post-ISIS strategy for stabilizing Iraq and Syria.

For all President Trump’s bombast about obliterating the Islamic State, also known as ISIS, the Raqqah campaign has been delayed for months while U.S. policymakers debated the wisdom of relying on a Syrian Kurdish militia known as the YPG that Turkey regards as a terrorist group. That group and allied Sunni fighters have been poised less than 10 miles from Raqqah, waiting for a decision.

All the while, the clock has been ticking on terror plots hatched by ISIS and directed from Raqqah. U.S. officials told me a few weeks ago they were aware of at least five ISIS operations directed against targets in Europe. European allies have been urging the U.S. to finish the job in Raqqah as soon as possible.

The horrific Manchester bombing is a reminder of the difficulty of containing the plots hatched in ISIS — and the cost of waiting to strike the final blows. ISIS is battered and in retreat, and its caliphate is nearly destroyed on the ground. But a virtual caliphate survives in the network that spawned Salman Abedi, the alleged Manchester bomber, and others who seek to avenge the group’s slow eradication.

The Raqqah assault should move ahead quickly, now that the Trump administration has rejected Turkish protests and opted to back the YPG as the backbone of a broader coalition known as the Syrian Democratic Forces. These are committed, well-led fighters, as I saw during a visit to a special forces training camp in northern Syria a year ago.

The Trump administration listened patiently to Turkish arguments for an alternative force backed by Ankara. But the Pentagon concluded that this force didn’t have any real battlefield presence, and that the real choice was either relying on the Kurdish-led coalition to clear Raqqah or sending in thousands of U.S. troops to do the job.

The White House rightly opted for the first approach several weeks ago. To ease Ankara’s worries, the U.S. is offering assurances that the Kurdish military presence will be contained, and that newly recruited Sunni tribal forces will help manage security in Raqqah and nearby Deir el-Zour.

The endgame is near in Mosul, too. Commanders say that only about 6 percent of the city remains to be captured, with 500 to 700 ISIS fighters hunkered down in the old city west of the Tigris River.

Once Raqqah and Mosul are cleared, the challenge will be rebuilding the Sunni areas of Syria and Iraq — with real governance and security — so that follow-on extremist groups don’t quickly emerge. This idea of preparing for the “day after” ISIS has gotten lip service from U.S. policymakers for three years, but very little serious planning or funding. It should be an urgent priority for the U.S. and its key Sunni partners, such as Jordan, Egypt, Saudi Arabia and the United Arab Emirates.

Intelligence services from several key allies are said to have met in recent weeks with Sunni leaders from Iraq to form a core leadership that can take the initiative. But so far, this effort is said to have produced more internal bickering than clear strategy — a depressing rewind of failed efforts to build a coherent Sunni opposition in Syria.

CIA Director Mike Pompeo told me and several other journalists in an interview Tuesday that he plans to move the agency to a more aggressive, risk-taking stance. Here’s a place to start.

The Kurds are the wild cards in both Iraq and Syria. The Syrian Kurds are already governing the ethnic enclave they call “Rojava.” That should be an incentive for Syria’s Sunnis to develop similar strong government in their liberated areas. Meanwhile, Iraqi Kurds have told U.S. officials they plan to hold a referendum on Kurdish independence soon, perhaps as early as September.

U.S. officials feel a deep gratitude toward Iraqi Kurds, who have been reliable allies since the early 1990s. But the independence referendum is a potential flashpoint, and U.S. officials may try to defer the Kurdish question until well after Iraqi provincial elections scheduled in September.

Iraq and Syria need to be reimagined as looser, better governed, more inclusive confederal states that give minorities room to breathe. The trick for policymakers is to make the post-ISIS transition a pathway toward progress, rather than a continuation of the sectarian catastrophe that has befallen both nations.

David Ignatius’ email address is davidignatius@washpost.com.