Hague said the country must form an inclusive government across sectarian lines to unite Iraqis against the Islamic State of Iraq and the Levant, or ISIL.
According to a statement from his office today, Hague said the militant group that has seized swathes of Iraq was a "mortal threat" to the country and threatened others in the region.
Britain has ruled out military intervention, but Hague said it would provide "diplomatic, counter-terrorism and humanitarian support."
Hague is due to meet with embattled Prime Minister Nouri Al-Maliki, Kurdish regional President Masoud Barzani and other political figures.