Iraq's prime minister will seek President Barack Obama's help to acquire billions of dollars in drones and other U.S. arms to fight the Islamic State group during a U.S. visit this week, a senior Iraqi official said.

Facing a cash crunch due to a plunge in oil prices and a budget deficit of roughly $21 billion this year, Prime Minister Haidar al-Abadi wants to defer payment for the purchases, said the official who spoke on condition of anonymity.

Al-Abadi is grappling with an insurgency by militants from Islamic State group, an al-Qaida offshoot that emerged from the chaos in Iraq and neighboring Syria and seized much of northern and central Iraq last year.