Ministers have also agreed to send Chinook helicopters to help with the aid effort.
David Cameron has been urged not to stand by amid "ethnic cleansing" in Iraq and recall MPs to vote on UK military intervention.
The call came in a letter to the Prime Minister, who is still on holiday in Portugal, from one of his own backbenchers, Conor Burns, as United Nations human rights experts warned that the world must take all possible measures to prevent a massacre of minorities in the country.
Mr Burns was one of a number of Tory, Labour and Liberal Democrat MPs who demanded greater action yesterday. Among them was former LibDem leader Sir Menzies Campbell, who said that the Coalition Government would be well advised to recall parliament and keep an open mind on military action.
But demands for MPs to debate intervention were ruled out by the Foreign Secretary Philip Hammond.
Thousands of people are still trapped on a mountainside in Northern Iraq, many without food or water, after fleeing from Islamic State (Isis) jihadists.
The UK has already sent Tornado fast jets to Iraq to work in a surveillance role to help with the aid effort.
An extra £3 million will be given to charities supplying humanitarian aid to more than 100,000 people in northern Iraq.