The U.S. government has begun to funnel weapons directly to Kurdish forces fighting Islamist militants in northern Iraq, U.S. officials said Monday, deepening American involvement in a conflict that the Obama administration had long sought to avoid.

The decision to arm the Kurds, via a covert channel established by the CIA, was made even as Pentagon officials acknowledged that recent U.S. airstrikes against the militants were acting only as a temporary deterrent and were unlikely to sap their will to fight.

“I in no way want to suggest that we have effectively contained, or that we are somehow breaking, the momentum of the threat,” said Army Lt. Gen. William C. Mayville Jr., the director of operations for the Joint Chiefs of Staff.

In a reflection of the administration’s reluctance to fight another full-fledged war in Iraq, Mayville said there are no plans to expand the limited air campaign, which President Obama ordered last week to prevent the massacre of Iraqi minorities and to protect U.S. military and diplomatic personnel in the northern city of Irbil.

U.S. military officials said they have conducted 17 airstrikes — including four on Monday — against fighters from the Islamic State, a jihadist group that has swept across northern Iraq in recent months and controls large parts of Syria. Mayville added, however, that the militants have responded by melting into populated areas, making it harder to target them.

The U.S. military released a video of targeted airstrikes in northern Iraq over the weekend. (YouTube: CENTCOM)

“They’re very well organized,” he said. “They are very well equipped. They coordinate their operations. And they have thus far shown the ability to attack on multiple axes. This is not insignificant.”

The Islamic State has an estimated 10,000 fighters and has routed Iraqi army units across much of the country, seizing large quantities of weapons and ammunition originally supplied to Baghdad by the U.S. government. In recent weeks, the group has overwhelmed the semiautonomous Kurdish security forces, surprising officials in Washington with the speed and breadth of its territorial advances.

Kurdish leaders have complained that they are outgunned and unable to mount a counter­offensive without more U.S. assistance.

American officials have tried to expedite the transfer of arms from the government in Baghdad to Kurdish fighters in the north. But that process has gone slowly, prompting Washington to open a direct pipeline to the Kurds via the CIA, according to two U.S. officials who spoke on the condition of anonymity because the spy agency has not publicly acknowledged the operation. The CIA declined to comment.

A U.S. military official said that the Pentagon and the State Department are discussing other possible ways to deliver weapons to the Kurds through open channels, but that they would need the legal authorization to do so. U.S. arms sales normally are restricted to sovereign or central governments.

Compounding the problem has been the eruption of political chaos in Baghdad, where Prime Minister Nouri al-Maliki has refused to relinquish power despite a U.S.-backed effort to replace him. Maliki has accused his domestic opponents of trying to oust him in a coup and has declined to recognize attempts to appoint a new prime minister.

A former U.S. military official who still works closely with the Kurds described the U.S. arms pipeline as “a trickle” that has been limited to Kurdish forces in the vicinity of Irbil. “They need everything, especially heavy weapons,” the former official said.

Some military analysts said that the effort to arm the Kurds and the administration’s limited airstrikes were unlikely to make much of a difference in the overall campaign against Islamist insurgents in Iraq.

“At most this will move the front lines at the margins,” said Stephen Biddle, a professor at George Washington University and frequent adviser to the Pentagon. “This war is headed for a Syria-like stalemate.”

Douglas Ollivant, a former U.S. military planner in Baghdad, said the shipment of mostly small arms and ammunition to the Kurds, combined with the cover of U.S. air power, should be enough to halt the advance of Islamic State fighters in the near term.

The group’s artillery cannons and armored vehicles — captured from the Iraqi army — should be especially vulnerable to airstrikes. “My guess is that the [insurgents] are going to lose a lot of equipment over the next couple of days,” said Ollivant, a fellow at the New America Foundation in Washington.

But analysts said it is unlikely that the Kurdish security forces, known as the pesh merga, will be able to mount a counteroffensive or make significant gains, even with the backing of U.S. warplanes. The events of recent weeks, they said, suggest that the Kurdish forces aren’t as capable or effective as U.S. officials may have assumed. “The pesh haven’t really fought anybody for a long time,” Ollivant said.

Mayville, the Army general, said the U.S. airstrikes were intended only to prevent Islamic State fighters from gaining more ground near Irbil or from advancing on Mount Sinjar, where thousands of people from the minority Yazidi faith have sought refuge amid fears of a massacre.

He said that, since Thursday, U.S. and British airdrops have provided Yazidi refugees on the mountain about 16,000 gallons of water and 75,000 meals, as well as medical supplies.

On Saturday, Obama said the U.S. government was discussing with allies whether they could establish a safe corridor so that the Yazidis could leave the mountain and return home, or seek haven in protected camps.

On Monday, however, Mayville said the Pentagon was unsure how many refugees were still on the mountain and indicated that no immediate plans were in the works to help relocate them. “What we’re going to need is a better understanding of what’s going on up there,” he said.

In addition to the airstrikes, U.S. military officials have said they are conducting 50 to 60 reconnaissance flights a day over Iraq to get a clearer picture of the refu­gee crisis and movements by Islamic State fighters.

Greg Miller contributed to this report.