Britain will discuss possibilities with US, including joining in air attacks in Iraq, and chance of rescue attempt for threatened Brit

The United States and Britain will discuss a range of military options for tackling Islamic State (Isis) at the Nato summit, opening in Wales on Thursday, ranging from joining in air attacks in Iraq and possibly Syria, to providing more arms to the Kurds and Iraqi government forces fighting them on the ground.

The British military will also discuss internally and with its US counterparts, following their own failed attempt last month, the realistic chances of special forces mounting a rescue operation to save the Briton threatened by Isis with beheading.

On Wednesday, after a meeting of the government emergency group Cobra, the British foreign secretary Philip Hammond said the UK government had to discuss the wider threat posed to the British public as well as the individual British citizen under threat.

He said the British government was examining "various options" and would look at considering every option to protect the person under threat. The US, for its part, does not as a matter of course rule out raids. But US officials have played down the prospect of impending hostage-rescue missions, much as they have been wary of crafting new policy in response to the executions ahead of what they consider a considered and multilateral approach.

What are the options?

Special forces

The Ministry of Defence in London will be discussing with the head of British special forces the chances of mounting a rescue. Hammond mentioned special forces but cautioned that the US special forces had tried to rescue the first American beheading victim, journalist James Foley, and failed. The biggest problem, as the US found, was establishing where the hostages are being held.

An obstacle to a future hostage rescue mission is the unusual decision of the US to confirm the first one.

While US administration officials claimed that they would not have confirmed the mission - which took place within Syria earlier this summer - had several news organisations not already learned of it, some mused off the record that the confirmation nevertheless jeopardised the hostages' lives. Public recognition of clandestine raids deep within Isis-held territory is likely to have made Isis much more attentive to operational security and secrecy, particularly as US officials emphasised that they had "actionable intelligence" on Isis locations.

Expanding the US air strikes against Isis in Iraq

At the Nato summit, Barack Obama will ask the UK and other members to join its campaign of air strikes against Isis in Iraq.

British planes have already been involved in helping during the Yazidi humanitarian effort. Security experts are divided about how effective air strikes can be, particularly in the absence of ground forces positioned to capitalise on an adversary's displacement. The US has taken encouragement by the ability of Kurdish and Iraqi forces, aided by US airstrikes, to take the critical Mosul Dam away from Isis, which is said to continue to aim at retaking it.

A Kurdish peshmerga officer during fighting with Islamic State fighters in Kurdistan, Iraq. Photograph: Mohammed Jalil/EPA

Air power stopped the Isis advance in places such as the Mosul dam.

Security experts consider Isis vulnerable to airstrikes, but with significant limitations. Its tactics are more like a conventional military than a terrorist organisation, involving massed vehicular columns on the move - something that can be targeted and bombed, as at the Mosul Dam and now in Amerli. But the longer Isis consolidates its hold on Iraqi and Syrian territory, the more it intermingles with the general population, effectively daring the US to kill civilians from above. Some wonder how Isis will be dislodged without bloody house-by house fighting.

During the Iraq war, US forces facing a similar group near the Syrian border at Tal Afar, cut off the town with a large sand berm but still had to fight for control street by street, with a high casualty rate. Tal Afar holds a special place in the US military's memory of the Iraq war, as a proving ground for counterinsurgency that would be expanded upon during the Iraq surge.

Military action is problematic for the UK, where parliament voted last year against intervention in Syria. But Lord West, the former sea lord and security adviser to the last Labour government, argued on Wednesday that the situation is now different: "They [Isis] are threatening British nationals and they have said they wish to destroy the British state. This is very different from looking at bombing Assad. Very different. They have said they want to kill British nationals. Assad never said that. The reason we have military forces is to stop people doing that. So the military can be part of that totality."

Speaking outside a Royal United Services Institute conference on Nato, Lord West said: "We need a properly coordinated package with the Americans to stop these abhorrent people and effectively take them out. And that is what we should do.

"You use special forces, drones, work with Americans, targeted air strikes, a mass of things, cut off their money, which could have an impact. So it is package of all of these things. It is quite a complex thing."

Air strikes against Isis in Syria

Obama said he has not yet decided whether to extend the bombing of Isis to Syria and this will be one of the dominant issues as Nato security experts argue that it makes no sense to confine bombing to Iraq as Isis does not recognise the border between Iraq and Syria, its forces moving freely across it. The US has already said that the border is now non-existent.

Nato has formally ruled out involvement in Iraq and Syria and the US will be pressing individually for other countries to join it in a new coalition of the willing.

The one major problem is that by attacking Isis in Iraq, the US is effectively intervening on the side of the Syrian president Bashar al-Assad, consolidating his power. Last year, Obama nearly went to war with Assad after the dictator used chemical weapons to kill hundreds of people in the Damascus suburbs of Ghouta.

Barack Obama speaks in Tallinn, Estonia, on the eve of the Nato summit. Photograph: Valda Kalnina/EPA

The chairman of the US joint chiefs of staff, General Martin Dempsey, said Isis will have to be dealt with in both Iraq and Syria, but, consistent with his years-long reluctance to signing onto the bloody Syrian civil war, has stopped short of endorsing cross-border operations. Dempsey has also said Isis is containable in the short term, causing confusion as to US goals in confronting the group. The US has drones flying over Syria collecting intelligence.

Joining the US in such strikes would be a political problem for Britain given that the debate last year was specifically about bombing Syria. Such an action now could be seen as a contravention of the will of parliament.

Arms exports

Britain could opt for helping the groups already engaged against Isis in Iraq, the Kurds and the Iraqi army.

There has been initial reluctance to provide too much assistance for fear of creating too strong a force in the Kurdish area leading to the break-up of Iraq and, for much the same reason, helping a Shia-dominant force in Baghdad.

But given public reluctance to put British boots on the ground in Iraq – unless the beheadings see a change in public opinion – this is one of the easiest options.

Whatever the British reluctance, the Pentagon has enthusiastically praised the UK for agreeing to arm the Kurdish Peshmerga. Britain was among seven nations that the US announced last week would rush small arms and ammunition to the Kurds' militia force. US Defense Secretary Chuck Hagel cited the agreement as evidence that the international coalition against Isis is growing.

Rear admiral John Kirby, the Pentagon press secretary, said on Wednesday that the US military remained in talks with its British counterparts about increased contributions against Isis.

The US and the UK could also try to persuade some of the regional powers to become involved and combine this with diplomatic pressure on Saudi Arabia and Qatar to stop financial support going to Isis.

Reform of Iraqi military and arming anti-Isis rebels in Syria

Despite a decade and billions of dollars already sunk into crafting a local fighting force in Iraq, the Pentagon is considering yet another revamp of the disappointing Iraqi military.

Hundreds of US special forces "advisers" are embedded in operations centers in Baghdad and Irbil to aid in planning for what has coalesced into a Kurdish and Iraqi counteroffensive on the ground in northern Iraq. Kirby acknowledged last week that an option under Pentagon consideration is to expand that into "more of an advisory mission," which typically involves placing troops directly into frontline units to shore them up. A complication for that option is continued blurring of Obama's oft-repeated prohibition on placing "combat troops on the ground" in Iraq.

The Obama administration has now decided the US military ought to engage in a similar effort to turn vetted Syrian anti-Isis, anti-Assad rebels into a credible fighting force. It represents a professionalisation of a year-long CIA operation aimed at running guns to them. Yet current and ex-officials vary in their assessment of how viable an option those Syrian forces remain against a far more experienced, larger and capable Isis foe. Nor has the US Congress approved the $500m the administration wants to launch the operation.

But at least one advantage, former intelligence officials said, is that propping up a Syrian fighting force will gain the US new sources of intelligence on the ground in a confusing battlefield.