The secretary of state had "matter-of-fact" talks with his Iranian counterpart despite disagreements.
The UN has passed a resolution to investigate war crimes committed by IS against the Yazidi people.
The area, west of Kirkuk, is one of so-called Islamic State's last two strongholds in Iraq.
What will happen to the Iran nuclear deal?
Being a girl guide in war-torn Syria
What's at stake in Iraqi Kurds' independence vote
What long list of Saudi gifts to Trump really mean
What happens when Islamic State leaves?
Father's daring journey to Syria to save his children
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