US Defence Secretary Ashton Carter arrived in Arbil on Thursday for talks with Iraqi Kurdish officials on the war against ISIS, an AFP journalist said.
Iraqi Kurdish forces are a key US partner in the war against ISIS, which overran large parts of Iraq last year.
Carter's visit to Arbil, the capital of Iraq's autonomous Kurdish region, followed a trip to Baghdad the day before.
There, he met Prime Minister Haider al-Abadi, and the two discussed "improving cooperation between the two countries in the fields of arming and training," a statement from the premier's office said.
Carter and his delegation also met US partners in the international anti-IS coalition.
US aircraft carry out daily air strikes against ISIS targets, most of them in the Iraqi part of the jihadists' self-proclaimed "caliphate", which also covers regions in Syria.
President Barack Obama said on Monday the US and its allies were hitting ISIS"harder than ever" and warned the extremists' leaders: "You are next."