As Shiite militia and Iraqi security forces gathered outside Ramadi, Iraq, for a counterattack against the Islamic State, which took over the city last weekend, the Obama administration debated what it could do to improve their chances of retaking the city.

The United States has expedited shipment to Iraqi forces of 1,000 additional AT4 anti-tank weapons of a type that previously has been used to great effect by the peshmerga, the Kurdish fighters in northern Iraq.

Iraqi Prime Minister Haider al-Abadi pleaded for more of the shoulder-launched, short-range missiles during his visit to Washington last month, for use against the massive vehicle bombs used by militants in Ramadi. The weapons are expected to arrive in Iraq by early June.

Other possible changes to administration policy, including the use of forward spotters on the ground to assist targeting by U.S. and coalition airstrikes, are more problematic.

President Obama has prohibited any combat role for the 3,000 U.S. troops in a train-and-assist capacity in Iraq, and U.S. officials have said that includes joint terminal attack controllers, or JTACs, who relay real-time information to nearby attack aircraft.

The Islamic State now controls Ramadi, a major city in Iraq. Here's why that matters and what to expect next. (Alice Li/The Washington Post)

Although U.S. warplanes have made numerous bombing runs near Ramadi in recent weeks, their efforts have been hindered by a lack of immediate precision targeting information. If they are to be effective in the future, some U.S. officials have argued, they need spotters on the ground.

In the absence of U.S. personnel, Iraqis are being trained to act as spotters, but there are concerns that enough of them cannot be sufficiently prepared to make a difference in Ramadi and elsewhere. In January, Canada said that its special operations forces participating in the coalition had moved to forward spotting positions on the front lines with Iraqi forces and had exchanged fire with Islamic State fighters.

High-level consideration of U.S. options came as Republican critics of the administration’s Iraq policy described the Ramadi defeat as a result of Obama’s weakness and indecision.

Sen. John McCain (R-Ariz.), chairman of the Armed Services Committee, said on the Senate floor that it “should lead our nation’s leaders to reconsider an indecisive policy and a strategy that has done little to roll back” Islamic State advances in Iraq and Syria.

The administration has charged that Iraq’s problems are rooted in mistakes made by Obama’s predecessor, President George W. Bush, beginning with the 2003 U.S.-led invasion that created a power vacuum and allowed al-Qaeda to gain a foothold now exploited by the Islamic State. Republicans, however, are attempting to shift the debate by saying that Bush eventually altered his policy and sent additional U.S. forces into Iraq. “Bush made his fair share of mistakes, but he adjusted,” said Sen. Lindsey O. Graham (R-S.C.), who is mulling a 2016 presidential bid.

“We need more of us on the ground to help [the Iraqis] and turn the tide of battle before ISIL gets even stronger and hits us here,” Graham said on the Senate floor, using an abbreviation for the Islamic State.

In a briefing for reporters Wednesday, a senior State Department official estimated that as part of an offensive beginning late last week, the militants set off about 30 suicide vehicle bombs in the city center within 96 hours, 10 of them with the explosive punch of the 1995 Oklahoma City bombing. In some cases, the official said, the vehicles involved were armored dump trucks, bulldozers and Humvees that were impervious to Iraqi defensive weapons.

Iraqis leave the city of Ramadi on Wednesday, May 20. Thousands fleeing violence in Anbar province poured into Baghdad province after the central government granted them conditional entry, a provincial official said. (Karim Kadim/AP)

“We’re still trying to piece together exactly what happened” with the retreat of Iraqi forces, said the official, speaking on the condition of anonymity under State Department ground rules.

But he said the situation in Ramadi was not as dire as last year’s Islamic State takeover of the northwestern Iraqi city of Mosul, where U.S.-trained Iraqi troops and police abandoned their posts and shed their uniforms before fleeing. After they were pushed out of Ramadi, government forces retreated to three points to consolidate, regroup and reequip, he said, and U.S. officials are working “around the clock” to assist them.

Col. Pat Ryder, a spokesman for the U.S. Central Command, told reporters in a Pentagon briefing that Iraqi forces would retake Ramadi, but he declined to give a timeline for an offensive.

Meanwhile, the State Department official said that coalition aircraft conducted strikes Wednesday in Ramadi, where the streets were largely barren, and that pilots were working to prevent the Islamic State from setting up defensive positions in and around the city.

The official praised Abadi’s response, including increased arming and training of tribal fighters in Anbar province, of which Ramadi is the capital.

In response to a call from Anbar’s provincial council, Abadi has sent thousands of Shiite militia forces to a mobilization point between Ramadi and the city of Fallujah, 50 miles west of Baghdad and also held by the Islamic State.

U.S. officials have insisted that the militias, whose presence was previously resisted by the Sunni tribes in Anbar, will be fully under the command of the Iraqi military.

Missy Ryan contributed to this report.