WASHINGTON (Reuters) - U.S. President Barack Obama and Italian President Sergio Mattarella met on Monday in the White House and discussed efforts to work together to combat the Islamic State in Libya. During a meeting in the Oval Office, Obama and Mattarella talked about the need to help Libya form a united government. “That will allow us to help them build up their security capacity and to push back against efforts by ISIL to gain a foothold in that country,” Obama told reporters after the meeting, using an acronym for Islamic State.  Islamic State forces have attacked Libya’s oil infrastructure and taken control of the city of Sirte, exploiting a power vacuum in the North African country where two rival governments have been battling for supremacy. Obama and Mattarella also discussed the refugee crisis facing Europe and the situation in Iraq and Syria. 