BAGHDAD/ DAMASCUS - Shiite Iran offered Saturday to consider working with long-time foe Washington if it takes the lead in helping repel Sunni Arab militants who have seized a swathe of northern Iraq.The offer came as Iraqi commanders said soldiers had recaptured two towns north of Baghdad as they prepared a fightback, bolstered by thousands of Shiite volunteers who answered a call to arms by top cleric Grand Ayatollah Ali al-Sistani. Prime Minister Nuri al-Maliki visited the besieged shrine city of Samarra north of the capital Friday to rally troops and pray at the Al-Askari mausoleum, a revered Shiite shrine whose 2006 bombing by Al-Qaeda sparked sectarian conflict that killed tens of thousands.President Barack Obama said he was ‘looking at all the options’ to halt the offensive that has brought jihadist-led militants within 50 miles (80 kilometres) of Baghdad city limits, but he ruled out any return of US combat troops. ‘We will not be sending US troops back into combat in Iraq, but I have asked my national security team to prepare a range of other options that could help support Iraqi security forces,’ he said.Obama has been under mounting fire from his Republican opponents over the swift collapse of the Iraqi security forces, which Washington spent billions of dollars training and equipping before pulling out its own troops in 2011. Iranian President Hassan Rouhani, who since taking office last August has overseen a rapprochement with a superpower Tehran long derided as the ‘Great Satan’, said his government was prepared to consider offering help.‘If we see that the United States takes action against terrorist groups in Iraq, then one can think about it,’ Rouhani told a news conference. Iraq's Shiite premier said the cabinet had granted him ‘unlimited powers’ to reverse the offensive, in which militants swept down towards Baghdad after overrunning second city Mosul on Tuesday before losing some of its steam.Troops found the burned bodies of 12 policemen as they recaptured the town of Ishaqi in Salaheddin province from Sunni Arab insurgents, police and a doctor said. It was one of the closest points to the capital that the militants reached in the offensive that saw them overrun a large part of northern and north-central Iraq this week. Troops also retook the nearby Muatassam area of Salaheddin, the colonel said.The United States has ordered an aircraft carrier, the USS George H.W. Bush, into the Gulf in response to the crisis in Iraq, the Pentagon said Saturday. ‘The order will provide the commander-in-chief additional flexibility should military options be required to protect American lives, citizens and interests in Iraq,’ Rear Admiral John Kirby, the Pentagon spokesman, said.Ordered by Defense Secretary Chuck Hagel, the move comes amid calls for air strikes to blunt a lightning offensive by Sunni Islamic militants that threatens Baghdad and the country’s Shiite-led government. US President Barack Obama said Friday the United States would not send in US ground troops but that he was weighing all other options.The Bush is being accompanied by two other warships - the guided-missile cruiser USS Philippine Sea and the guided-missile destroyer USS Truxtun, Kirby said in a statement. The carrier’s movement into the Gulf from the north Arabian Sea was expected to be completed by the end of the day, he said. ‘American naval presence in the Arabian Gulf continues to support our longstanding commitments to the security and stability of the region,’ he added.On Friday night, police and residents expelled militants from another town in the province, Dhuluiyah, where they had set up checkpoints, witnesses said. ‘Residents are now firing into the air’ in celebration, witness Abu Abdullah told AFP. Security forces have also held fast in the Muqdadiyah area of Diyala province, preventing militants from taking the town in heavy fighting, a police colonel said.In Samarra, reinforcements were awaiting orders to launch a counter-offensive against areas north of the city, including Dur and Tikrit, seized by the militants earlier this week, an army colonel said. North of Baghdad, gunmen on Saturday attacked a convoy carrying the head of the anti-corruption watchdog, sparking clashes that killed nine policemen, an officer said.Security forces have generally performed poorly, with some abandoning their vehicles and positions and discarding their uniforms. But they have been bolstered by a flood of volunteers since Sistani urged Iraqis Friday to join up to defend the country.Moreover, soldiers armed with shovels are digging in just 25 kilometres (15 miles) north of Baghdad as others man new checkpoints, bolstering the Iraqi capital's defences against a militant assault.A major militant offensive launched, spearheaded by Iraq and the Levant (ISIL) group but also involving supporters of executed dictator Saddam Hussein, has overrun a large chunk of northern and north-central Iraq. The advance swept to within less than 100 kilometres (60 miles) of the capital, raising fears among residents that the city itself would be next, though militants have since been pushed back by security forces in areas farther north, making an assault on Baghdad appear less likely.ISIL spokesman Abu Mohammed al-Adnani has vowed its fighters would press on to Baghdad and Karbala, a city southwest of the capital that is considered one of the holiest sites in Shiite Islam. Top Shiite cleric Grand Ayatollah Ali al-Sistani on Friday urged Iraqis to take up arms against the Sunni militants.Moreover, a bomb attack targeting a weapons bazaar in eastern Syria near the Iraqi border killed 30 ‘terrorists’ on Saturday, state television reported. ‘A big explosion hits a terrorist arms market in Mayadeen, killing 30 terrorists and wounding dozens of others,’ the channel reported. The Syrian Observatory for Human Rights gave a different account, alleging a ‘bomb planted in the car of an arms dealer’ caused a series of blasts, as nearby munitions exploded.‘At least eight civilians were killed and 21 others were wounded,’ said the Britain-based group, which distributed amateur video showing burnt corpses. Just 80 kilometres (50 miles) from the Iraqi border, the town is under the control of rebel groups, including Al-Qaeda's Syria affiliate the Al-Nusra Front, that have been fighting the jihadist Islamic State of Iraq and the Levant.ISIL is the same cross-border group which has spearheaded a lightning offensive in neighbouring Iraq this week that has seen militants sweep down from second city Mosul towards Baghdad. A rebel spokesman from Syria's Deir Ezzor province contested the state television version, and told AFP the blast was a car bomb planted by ISIL that killed at least 15 civilians in a street market. The rise of Al-Qaeda-linked militants in Iraq can be traced to America's invasion of the country more than a decade ago, as it left a power vacuum and unleashed sectarian bloodletting, experts said Friday.With television footage of Sunni extremists sweeping across Iraq this week, critics of former president George W. Bush's decision to invade in 2003 said the onslaught offered yet more proof of the war's disastrous fallout.Neoconservatives who backed Bush's decision touted the war as a way to build a model for democracy in the Middle East. Instead, it has fueled an explosive Sunni-Shiite divide that is still sending shockwaves through the region, experts said.