He is meeting US ambassador in Iraq Ryan Crocker and military leader General David Petraeus, as well as key Iraqi officials including prime minister Nouri al-Maliki and president Jalal Talabani.
The latest visit comes after US forces in the country experienced their most deadly month since the 2003 invasion, with more than 100 troops killed in April alone.
Mr Cheney is hoping to be reassured of the Iraqis' resolve to maintain security in the country, in particular in the volatile capital Baghdad, but a bomb in the northern city of Irbil during the visit emphasised the difficulty of that task.
At least 19 people are thought to have died after a suicide truck bomb hit the interior ministry in the predominantly Kurdish city this morning.
Another 80 were injured, the Associated Press news agency cites local officials as saying, and insurgents have been blamed for the blast.
Irbil is more than 200 miles from Baghdad and is situated in what is considered to be one of the safer areas of Iraq.
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