US President Barack Obama is considering faster training and more arms supplies for Iraqi tribes, while eying a rapid counteroffensive to retake Ramadi from the Islamic State of Iraq and Levant (ISIL), a US official has said.

"We are looking at how best to support local ground forces in Anbar [province]," Alistair Baskey, National Security Council spokesperson, told AFP news agency, "including accelerating the training and equipping of local tribes and supporting an Iraqi-led operation to retake Ramadi."

Ramadi, a city in Iraq's Sunni heartland just 90 minutes' drive away from the capital Baghdad, was taken by ISIL on Sunday.

Iraq's army and allied militias are currently massed around Ramadi, looking for swift action to recapture the city from ISIL before it builds up defences.

The UN said on Tuesday that at least 25,000 people had escaped the city ahead of the expected battle.

The audacious military victory was a major blow in the battle against ISIL, calling into question Obama's strategy in Iraq and the authority of his ally, Prime Minister Haider al-Abadi.

Ramadi, a city in Iraq's Sunni heartland just 90 minutes' drive from Baghdad, was captured by ISIL on Sunday [Zeina Khodr/Al Jazeera]

The White House has described the loss of Ramadi as a "setback" but played down suggestions that the war is being lost.

"Are we going to light our hair on fire every time that there is a setback in the campaign?" asked White House spokesman Josh Earnest.

"There is no formal strategy review," said Baskey, indicating that the pace rather than type of assistance to Sunni tribes was in question.

A more detailed announcement could come within days.

Obama has repeatedly ruled out sending vast numbers of US troops back to the theatre of a bloody and unpopular nine-year war that he vowed to end.

Instead, he has vowed to support Iraq's struggling army and hit ISIL from the air.

Uneasy over arms flow

There has been a rise in support for disparate Iraqi militias that have proven a more potent fighting force than army or police regulars.

Both Washington and Baghdad had been uneasy about arms flowing directly to Kurdish peshmerga fighters in the north, fearing those arms could later be used in the battle for independence.

Meanwhile, many of the Shia groups that helped retake Tikrit are armed and trained by Iran.

The White House wants to see those groups firmly under the command and control of the Iraqi military, but is also turning to Sunni tribes, which helped turn the tide of America's own war in Iraq through the "Sunni Awakening."

But reeling from the worst setback since ISIL grabbed swathes of territory in June last year, Abadi called in the Shia-dominated Popular Mobilisation units for help.

The UN says at least 25,000 people have escaped Ramadi in advance of the expected battle for the city [Zeina Khodr/Al Jazeera]

Source: Al Jazeera and agencies