Visiting US Vice President Dick Cheney on Monday said the United States has made a "successful endeavor" in Iraq on the eve of the fifth anniversary of the US-led invasion.

Cheney, who arrived in Baghdad in the morning on an unannounced visit, met Iraqi Prime Minister Nuri al-Maliki and other Iraqi political figures.

Iraqi Prime Minister Nuri al-Maliki (R) shakes hands with US Vice President Dick Cheney in Baghdad March 17, 2008. (Xinhua/Reuters Photo) 

He said there was a significant progress compared with 10 month ago when he was traveling here, adding security has improved dramatically and the Iraqi leaders have made progress in governing.

Yet, he pointed out that "it's clear there is still a number of major issues that need to be addressed."

Cheney made the trip three days ahead of the fifth anniversary of the Iraq war that falls on March 20.