NAPLES, Italy — The United States is considering establishing a new network of military bases in Iraq to aid in the fight against the Islamic State, senior military and administration officials said Thursday, potentially deepening American involvement in the country amid setbacks for Iraqi forces on the battlefield.

Speaking to reporters aboard his plane during a trip to Italy, the chairman of the Joint Chiefs of Staff, Gen. Martin E. Dempsey, described a possible future campaign entailing the establishment of what he called "lily pads" — U.S. military bases around the country from which trainers would work with Iraqi security forces and local tribesmen in the fight against ISIS.

Dempsey's framework was confirmed by senior Obama administration officials and comes after an earlier decision this week to send 450 trainers to establish a new military base to help Iraqi forces retake the city of Ramadi, the capital of Anbar province. The general said that base could be the model for a new network of U.S. training bases in other parts of the country.

"You could see one in the corridor from Baghdad to Tikrit to Kirkuk to Mosul," Dempsey said. Such sites, he said, could require troops in addition to the 3,550 that the president has authorized so far in the latest Iraq campaign, although he said later some of the troops at the new bases could come from forces already in Iraq.

For President Barack Obama, who spent much of his first term orchestrating the total withdrawal of U.S. combat troops from Iraq and for the past year has publicly resisted making major troop commitments there, establishing new U.S. bases within Iraq would be another step toward deeper entanglement in the country.

Further, the creation of persistent American-staffed bases in the Iraqi countryside would give ISIS obvious new targets, allowing it to expand its fight directly against U.S. forces — a possibility the group's propaganda operation has publicly reveled in.

Military officials acknowledge that the more U.S. troops there are on the ground in Iraq, the greater the incentive for ISIS militants to attack them.

There is already precedent: In February, eight suicide bombers who Defense Department officials said were with ISIS managed to get into an air base west of Baghdad where hundreds of U.S. Marines were training Iraqi counterparts. Although officials said the bombers were killed almost immediately by Iraqi forces, the assault was a reminder that even circumscribed training missions create a risk for American casualties.

The model for a potential new network of U.S. bases in Iraq is already being built at Taqaddum, an Iraqi base near the town of Habbaniya in eastern Anbar. The U.S. troops being sent are to set up the hub primarily to advise and assist Iraqi forces and to engage and reach out to Sunni tribes in Anbar, officials said. One focus for the Americans will be to try to accelerate the integration of Sunni fighters into the Iraqi army, which is dominated by Shiites.

While retaking the city of Ramadi, which fell to ISIS last month, is the goal of the training hub at Taqaddum, Dempsey indicated that this effort may be months away. While declining to put a timetable on when the battle to retake Ramadi will begin, he said it would take several weeks for the initial command and control center at Taqaddum to be set up.

"Timetables are fragile," Dempsey said. "They are dependent on so many different factors."

For the Pentagon, the timetable issue has been a tense one, as the U.S. Central Command and the Iraqi government have clashed in the past about the pace of efforts by the Iraqi security forces to retake areas captured by ISIS.

Obama has been loath to commit a large number of U.S. ground troops to Iraq. Administration officials say it is up to the Iraqi government to lead the way in reclaiming its territory and cities from the extremists, and the Shiite-dominated government can do so only by being more inclusive toward the country's Sunni minority.

Dempsey said the United States was still hoping the Iraqi government would find a way to engage Sunnis to beat back ISIS, but he also talked of what he called a "Plan B" in case that never happens.

"We have not given up on the possibility that the Iraqi government could absolutely be whole," he said but added that "the game changers are going to have to come from the Iraqi government itself."

"If we reach a point where we don't think those game changers are successful, then we will have to look for other avenues to maintain pressure on (ISIS), and we will have to look at other partners," he said.

Dempsey said that he does not envision another military base in Anbar but that Pentagon planners were already looking at more northern areas for additional sites.

The Obama administration is hoping that reaching out to Sunnis will reduce the Iraqi military's reliance on Shiite militias to take back territory lost to ISIS.

To that end, the Americans will send arms and equipment — including AK-47s and communications equipment — directly to Taqaddum. The supplies are to be transferred to Iraqi army units, which are then supposed to give them to Sunni fighters. U.S. military officials said U.S. soldiers would be there to ensure the transfer to Sunni fighters.

Officials said the Iraqi Security Forces were expected to do the bulk of the work to retake Ramadi once that campaign gets going. But once the city is reclaimed, it will probably be the Sunni fighters who will have to hold them.

"What the tribes are going to provide is not only thickening of the ranks of those fighting (ISIS), but at some point, the ISF will want to protect" the cities that have been liberated, Dempsey said. "The responsibility of defending the cities that are liberated — that will fall to the local tribes."