Dick Cheney has made an unannounced visit to Baghdad in what was said to be an effort to encourage reconciliation among rival factions.
A senior aide, who asked to remain anonymous, said the US vice-president's message would be: "We've all got challenges together. We've got to pull together. We've got to get this work done. It's game time."
Cheney is to meet Nuri al-Maliki, the country's prime minister, as well as Iraq's Kurdish president and its Sunni and Shia vice-presidents.
He was expected to tell the Iraqis that the current US military build-up is not enough on its own to end the conflict.
Before the unscheduled visit, Cheney's public schedule was for him to stop in the United Arab Emirates, before moving on to Saudi Arabia, Egypt and Jordan.
Parliament argument
US officials said Cheney's mission was to get a sense of the situation on the ground in Iraq and to give the message that more work was needed on the political front to overcome divisions and delays.
Cheney was briefed on conditions by General David Petraeus, the US commander in Iraq, and Ryan Crocker, the new US ambassador to Baghdad.
The discussions included a renewed request that the Iraqi parliament not take a two-month vacation.
Crocker said that urging the parliament to stay in session through these difficult times was clearly on the vice-president's agenda.
He said: "For the Iraqi parliament to take a two-month vacation in the middle of summer is impossible to understand."
Cheney was due to have lunch with al-Maliki and Iraqi officials and then have dinner with them at the US embassy.