The US is sending an aircraft carrier and two guided missile ships into the Persian Gulf, bolstering sea and airpower before a possible US strike on the jihadist army in Iraq in the coming days.

Defense secretary Chuck Hagel ordered the USS George HW Bush into the Gulf on Saturday, a day after President Barack Obama indicated he would soon decide on air strikes against the Islamic State of Iraq and the Levant (Isis), whose seizure of Sunni Iraqi cities has violently upended the region.

The 103,000-tonne warship and its air wing, which had been patrolling the North Arabian Sea and earlier this year were used in the Mediterranean following Russia's invasion of Ukraine, gives Obama airstrike options in addition to air force assets on land in bases used by the US, like Qatar's al-Udeid.

The Bush's air wing includes four squadrons flying F/A-18 Super Hornet fighter jets, one squadron flying EA-18 Growler jammer and electronic-attack planes, and other maritime helicopters and early-warning planes.



Rear Admiral John Kirby, the Pentagon press secretary, said the Bush would be accompanied by the guided-missile cruiser USS Philippine Sea and the guided-missile destroyer USS Truxton. The ships are expected to arrive in the Gulf this evening.



Kirby described the deployment as increasing Obama's martial flexibility "should military options be required to protect American lives, citizens and interests in Iraq", rather than signalling an imminent strike.



In a briefing on Friday, Kirby had played down the possibility of the Bush moving into the Gulf, saying only that it was ready for a potential tasking. "As we speak right now, there is no aircraft carrier zorching [speeding] into the Persian Gulf," he said.



While Iran has in the past harassed US ships moving into the Gulf, its president, Hassan Rouhani, on Saturday indicated openness to working alongside his country's decades-old adversary, signalling an alignment of interests in protecting their mutual Iraqi partner.



"If we see that the United States takes action against terrorist groups in Iraq, then one can think about it," Rouhani told reporters, according to Agence France Presse.



Iraqi officials told the Guardian on Saturday that Iran had sent 2,000 advance troops across the border to help the Shiite government of Iraq defend itself after the Iraqi army ran from Isis in Mosul this week. In a move unthinkable during the Saddam Hussein era, Iran has sent the commander of its feared Qods Force, General Qassem Suleimani, to coordinate the defense of Baghdad.



US intelligence and defense officials consider Suleimani to have American blood on his hands, as the Qods Force and the Revolutionary Guards Corps to which it belongs are suspected of attacks on US troops during the Iraq war, including the placement of sophisticated and deadly bombs.



Obama's contemplation of air strikes against Isis creates the prospect of US air power bolstering Iranian ground operations, an awkward one given the animosity the militaries of the two nations, which are currently engaged in negotiations over Iran's nuclear program, have long felt for each other.



The State Department did not immediately respond to queries about US and Iranian forces possibly fighting alongside one another by default in Iraq.

On Friday, Kirby urged Iran to "play a constructive role" in Iraq.

