WASHINGTON — U.S. military and intelligence officials are increasingly pessimistic about the prospects for political reconciliation in Iraq, a key tenet of the Obama administration’s strategy to dislodge the Islamic State group and stabilize the country.

Senior officials say they are not seeing significant progress by the country’s Shiite-led government on its efforts to strike a bargain with Iraq’s deeply alienated Sunni population, from which the extremist force is drawing money and personnel.

President Barack Obama expressed hope in September that a new Iraqi government led by Prime Minister Haider Abadi “understands that in order for Iraq to succeed it’s not just a matter of a military campaign; it’s also the need for political outreach to all factions within the country.” That’s a feat his predecessor, Nouri al-Maliki, didn’t achieve.

But in the months since, the Shiite-dominated government has taken few concrete steps to accommodate Sunnis, whose frustration helped fuel the Islamic State group’s push into Iraq from Syria.

Joint chiefs chairman Gen. Martin Dempsey, who returned from the region this week, told Congress Wednesday he was “concerned about what happens after the drums stop beating and ISIL is defeated, and whether the government of Iraq will remain on a path to provide an inclusive government for all of the various groups within it.” Dempsey used an alternative acronym for the militant group.

Director of National Intelligence James Clapper said on March 2, “I really don’t think there’s any way of reversing or changing the picture fundamentally in Iraq unless the Sunnis are included … and so far that’s been a struggle.”

Instead of reaching out to Sunnis, the Iraqi government has bolstered its already close ties to Iran and to Iranian-backed Shiite militias that have been credibly accused of massacring Sunnis, U.S. officials acknowledge. The Iraqi military’s reliance on Shiite militias this week to retake Tikrit, a Sunni stronghold, has complicated the prospects of political reconciliation, experts say.

Although some Sunnis welcomed the liberation force, the well-publicized role of the Iranian Revolutionary Guard’s Quds Force commander Qassem Soleimani in directing the assault on Tikrit has inflamed many Sunnis. Iran and Iraq fought a bloody seven-year war in the 1980s.