Britain has agreed to send military equipment to Kurdish forces fighting jihadists in northern Iraq to support US weapons which have already been delivered to the Peshmerga.

UK troops will transport Jordanian military trucks to Irbil in the semi-autonomous region of Iraqi Kurdistan.

London will also send helicopters to airlift Yazidi refugees besieged on Mount Sinjar after being forced from their homes by Islamic State extremists.

Washington has ordered 130 more military advisors to assess the humanitarian crisis unfolding but insists it is not about to send large troop numbers back to Iraq.

“This is not any extension of any role – for the United States – other than to find ways to assist and help advise the Iraqi security forces which we have been doing,” said US Defence Secretary Chuck Hagel, addressing American troops at Camp Pendleton in California.

The UN estimates as many as 30,000 minority Yazidis are trapped on Mount Sinjar and thousands more have crossed into Syria or reached Irbil.

On Wednesday, hours after Haider Al-Abadi was announced as Iraq’s new prime minister-designate after months of infighting, a suicide bomber struck at a checkpoint near his home in Baghdad.