Senior British officer dispatched to advise Kurdish forces, but no arms will be sent to Baghdad until it has formed government

The UK is to directly arm Kurdish forces fighting Islamic State militants in Iraq and has sent a senior military officer to advise them, prior to what may be a larger Nato-led operation in the region.

Britain has so far been a conduit for transporting non-lethal military equipment and ammunition sent by other countries, notably Albania, but has not itself sent firearms or munitions. On Wednesday, Britain delivered 10 tonnes of body armour, helmets and equipment. Albanian ammunition is needed since the Kurdish fighters have largely Russian-made hardware.

Britain has been one of the last western countries to offer to arm the Kurds with similar decisions already taken by Italy, France, the US, Australia and some smaller countries. British hesitation may have been in deference to objections from Turkey. The UK has been sending Tornados on reconnaissance missions.

Downing Street also confirmed that Lt Gen Sir Simon Mayall, the Ministry of Defence's Middle East envoy, had arrived in Irbil to act as the direct representative of the prime minister.

No 10 will not be sending arms to Baghdad until it has formed a government, due to completed by 11 September.

The removal of the previous sectarian Iraqi leader, Nouri al-Maliki, and his replacement by Haider al-Abadi followed intense lobbying by the Americans, especially the vice-president, Joe Biden. A No 10 spokesman said the Iraqis had been working to the date of 11 September for the formation of a new administration, but talks in Baghdad have been stalled as Sunnis, Shias and Kurds wrangle over splitting up the ministries.Sunnis have been looking for as many as 40%.

David Cameron made clear on Thursday morning that it was almost a precondition of further direct help to Baghdad that agreement is reached on its composition.

The Iraqis are at present involved in some of the most intense fighting in Tikrit, and are better armed than the Kurds. British sources said there had been a gradual effective pushback against Isis in the past few weeks.

There were reports that the Iraq parliament may meet in emergency session as early as Thursday evening to vote on the Abadi government, and if this occurred and agreement was reached, one of the preconditions for wider military help to Baghdad would be swept aside.

Cameron in his morning round of interviews said: "The need for a proper Iraqi government is so central to this. Above all, what we need is a functioning, stable and inclusive Iraqi government. This problem is at the heart of Iraq and the first thing that is required is an Iraqi government that represents all the people of Iraq.

"Indeed, one of the reasons this issue has come about is because we did not have an Iraqi government of that nature. The most important thing we need is a government in Baghdad that represents all of the Iraqi people. We must make sure that the help we give is in concert with those on the ground, rather than ignoring that they are there or going over their heads."