David Cameron defends 'clear' Iraq strategy
Prime Minister David Cameron has insisted the government's position on Iraq is "clear" and said the UK would not deploy "boots on the ground".
Mr Cameron said Britain would "use all the assets that we have", including "military prowess" and aid to defeat the "monstrous" Islamic State militant group (IS).
Parliament did not need to be recalled to discuss Iraq, he added.
Labour said Britain's role in the crisis was "pretty unclear".
Defence Secretary Michael Fallon has said the UK's military involvement in the country could last for "months", and has revealed that RAF surveillance aircraft are operating there.
IS, an extreme Sunni Islam group, is seeking to build a so-called caliphate - a new Islamic state spanning Iraq and Syria.
The group has seized large parts of both countries in recent months and is alleged to have carried out mass killings of non-Muslims.
Jonathan Beale, BBC defence correspondent
The British military role in Iraq has already morphed from providing humanitarian relief to gathering intelligence. It could easily change again to more direct intervention.
Even now one can assume that surveillance being carried out by the RAF's latest spy plane - the Rivet Joint - is being used to help the US military to identify potential IS targets.
The eight Tornado jets already at RAF Akrotiri in Cyprus, and currently being used for surveillance, could easily switch to a bombing role. But such a move would probably have to be approved by the Cyprus government.
The political language is changing - perhaps a sign that ministers are preparing the ground for airstrikes. The military hardware is in place. But there are still obstacles - not least consulting Parliament.
Mr Cameron, who warned in a Sunday Telegraph article at the weekend that IS could target the UK unless action is taken, told BBC Breakfast there was a "political and extremism crisis" in Iraq that had a "direct effect" on the UK.
He said: "Britain is not going to get involved in another war in Iraq. We are not going to be putting boots on the ground. We are not going to be sending in the British Army."
He said Britain would "use the assets that we do have" and work with its allies and the Iraqi government.
The government would "look favourably" on a request for arms from Kurdish fighters, he added.
Mr Cameron has faced demands to recall Parliament, which is on its summer break, to discuss Iraq, but he later said: "We are not contemplating things that would require that."
The government's Cobra committee met on Monday to discuss the situation in Iraq. Afterwards Foreign Secretary Philip Hammond said: "There's no call for us to deliver air strikes at the moment. The US is delivering targeted air strikes and they're perfectly able to do what needs to be done."
A Downing Street spokesperson added that the humanitarian situation in the region "remains dire".
On Sunday, Kurdish forces - aided by US air strikes - were reported to have regained control of the strategically important Mosul dam after ousting IS militants. The facility was seized by IS earlier this month.
Whitehall has confirmed UK military flights began ferrying ammunition from eastern European countries to the Kurdish Regional Government from last week. The supplies are for front-line forces battling Islamic State in northern Iraq.
Austria, France and Germany are also sending military supplies to the Kurds.
Mr Fallon told military personnel on a visit to RAF Akrotiri in Cyprus that the UK's role in Iraq had expanded beyond the original humanitarian mission to include intelligence-gathering.
"There may well now be in the next few weeks and months other ways that we may need to help save life [and] protect people and we are going to need all of you again and the surveillance you are able to give us," he said.
Mr Fallon said the RAF had now deployed the Rivet Joint surveillance aircraft alongside Tornado bombers to provide vital intelligence on IS movements across Iraq.
Troops from the 2nd Battalion Yorkshire regiment had been sent into the Kurdish capital Irbil for 24 hours to prepare the ground for a possible rescue mission by the helicopters.
They have now left but British special forces are still believed to be in northern Iraq.
Rivet Joint surveillance aircraft
Boeing RC-135W (Airseeker)
paid for three spy planes from US
3,900-mile range (6,500km)
131ft wingspan (40m)
21-27 mission crew: including up to 3 pilots, 2 navigators, maintenance technicians and intelligence operators
Mr Fallon said Britain could also provide equipment such as body armour and night-vision goggles to Kurdish forces.
For Labour, shadow foreign secretary Douglas Alexander said: "It is important to understand the nature of the mission that British forces are now engaged in."
He called for "clarity" from the government but added: "We have supported the steps that the British government, along with other European allies, have taken."
Labour MP Ann Clwyd, who was special envoy to Iraq during the Blair government, told BBC News more clarity is needed.
She said: "Nobody is very clear, listening to the reports, what is actually going on. Are there troops already on the ground or are there not?
"We know the RAF has been very active, are there intelligence people on the ground or are there not?"
She raised particular concerns about thousands of Yazidi women apparently kidnapped in Iraq, adding: "Surely the intelligence services in this country could be used to locate these women."
And she questioned Mr Cameron's decision to go on holiday again, saying his absence was not "satisfactory" and describing the situation as a "mess".
Mr Cameron has defended his latest holiday, saying: "Wherever I am, wherever I am in the world I am always within a few feet of a BlackBerry and an ability to manage things should they need to be managed."
Thousands of Christians and Yazidis have fled their homes to escape IS fighters. IS has also persecuted Shia Muslims, whom it does not regard as true Muslims.
Kurdish officials said the next objective was to clear IS fighters from the Nineveh plain, north-west of Baghdad, "to ensure the return of minorities".