The Pentagon indicated Monday that the US-built Iraqi security forces are on their own to recapture the western Sunni province of Anbar from al-Qaida fighters, who have taken control of key locations in the desert near the Syrian border.

Al-Qaida’s Iraqi-Syrian affiliate has declared control of Falluja, the site of two of the bloodiest battles of the nine-year US occupation. It is the latest escalation after some of the worst violence Iraq has experienced since 2007.

But as bitter as it may be within the Pentagon to see the black banners of al-Qaida above the buildings of a city where soldiers and marines twice fought house-to-house assaults, there is little appetite to recommit precious US military resources, and secretary of state John Kerry has ruled out the return of US troops to aid the Iraqis they once trained.

“We’re not doing tactical work with the Iraqis,” said army colonel Steve Warren, a Pentagon spokesman, who raised doubts about the severity of the past days events in Anbar.

“I don’t know that it’s as urgent as maybe some of the press reporting [indicated]”, Warren said. “Ramadi is back under Iraqi government control. The Iraqi army has yet to even really engage.”

As part of a $14bn program of military hardware sales begun in 2005, the Iraqis recently received 75 Hellfire air-to-ground missiles. A follow-on shipment will be expedited, as will the delivery of 10 ScanEagle unarmed surveillance drones. “We do share a lot of information,” Warren added.

But neither the new missiles nor the drones will finish arriving before the spring, the Pentagon said. An additional contingent of under 200 US advisers, the final cohort of US troops in Iraq following the December 2011 withdrawal, advises the security ministries and shares intelligence.

US officials have said they were willing to help bolster Iraq’s indigenous intelligence capabilities.

“We do want to help the Iraqis develop the capability to target these [terrorist] networks effectively and precisely,” a senior administration official said in October during a visit by Iraqi prime minister Nouri al-Maliki.

The CIA has reportedly been assisting Iraq with targeting militant networks. The CIA declined to comment on Monday.

Beyond that, the Iraqis must rely on the training, small arms, vehicles and other hardware that the US provided in rebuilding the military it defeated and then cashiered in 2003 following its invasion.

The tenuousness of the Iraqi government’s ability to confront levels of violence not seen since the darkest days of the occupation raises bitter questions about what the US actually purchased for the $60.6bn it spent rebuilding Iraq from 2003 to 2012; and particularly the $20.2bn it spent since 2005 building a new Iraqi army and police force from scratch.

Following Maliki’s Washington visit, the US provided Iraq last month with a cache of 75 Hellfire missiles. Criticized for not providing additional aid as a government backed by the US – and, awkwardly, Iran – and amid struggles to confront a rising tide of brazen attacks, the Obama administration has said Iraq did not formally ask for the resumption of armed US drone flights over its territory.

Maliki called on residents of Falluja to oust the forces of the Islamic state of Iraq and Syria, the al-Qaida regional affiliate, ahead of a campaign by his army, which reportedly had the city encircled Monday.

Maliki left Washington in October without several items of military hardware he wanted, some of which are valuable in counter-terrorism and counterinsurgency campaigns, such as Apache helicopters, and others that are not, such as air-defense missiles and F-16 fighter jets. The sale of the Apaches is pending before the US Senate, and in the interim, Iraq is acquiring a fleet of MI-28 and MI-35 helicopters from Russia.

US troops left Iraq in 2011 after Iraq rejected a basing accord due to concerns about US impunity for crimes committed in the country. Republican hawks have accused the Obama administration for not securing the deal, known as a status of forces agreement, but tend to overlook the Iraqi legislature’s role in rejecting a US troop presence.

“When President Obama withdrew all US forces from Iraq in 2011, over the objections of our military leaders and commanders on the ground, many of us predicted that the vacuum would be filled by America's enemies and would emerge as a threat to US national security interests. Sadly, that reality is now clearer than ever,” Senators John McCain and Lindsey Graham said in a statement over the weekend.

In November 2011, ahead of the troop withdrawal, army general Lloyd Austin, the final US commander in Iraq, warned that “al-Qaida will continue to do what it’s done in the past, and we expect that it’s possible they could even increase their capability.”

Austin, now the commander of all US troops in the Middle East and South Asia, added: “If the Iraqi security forces and the government of Iraq are able to counter that, it will be a good thing. If they can’t, they’ll continue to grow in capacity.”

For years, US military leaders publicly vouched for the performance and integrity of the Iraqi security forces they nurtured, trained and equipped. Yet the force remains riddled with sectarianism, incompetence and corruption, a microcosm of the persistent political divisions afflicting the country after the US overthrow of Saddam Hussein and subsequent occupation – all of which, according to a recent report from defense analyst Anthony Cordesman of the Center for Strategic and International Studies, provides al-Qaida with continuing opportunities in Iraq.

The Iraqi security forces “are both a path to stability and security and a threat to stability and security. They will remain so until Iraq has a more unified and truly national government,” Cordesman wrote Sunday.

“Moreover, unless outside aid take full account of the degree to which they are both a potential solution to Iraq’s violence, and its cause, increased effectiveness may push Iraq towards deeper civil conflict.”

The Pentagon’s Warren said Monday he was confident that the Iraqi army is a “very capable force”.