BAGHDAD, Iraq (CNN) -- Sen. John McCain arrived in Baghdad on Sunday, the U.S. Embassy confirmed, marking his first trip to the war-ravaged nation since becoming the presumed Republican candidate for president.
McCain traveled there with Sens. Lindsey Graham, R-South Carolina, and Joseph Lieberman, I-Connecticut, both of whom serve on the Armed Services Committee with McCain, the committee's ranking member.
The visit was unannounced for security reasons, but McCain's office had indicated he planned to go there.
The trip was McCain's eighth to Iraq since the U.S.-led invasion five years ago. 
Watch a report on the senator's visit »
All three senators are outspoken advocates of the "surge" strategy -- sending additional troops to Iraq -- and McCain has credited the strategy with reported dips in violence there.
Also, Graham and Lieberman are high-profile McCain supporters.
Critics question whether U.S. taxpayers are bankrolling a campaign junket. McCain campaign aides have openly said they hope the trip shows him to be authoritative and comfortable on the world stage.
McCain's response has been that members of the Armed Services Committee need to visit Iraq to get a first-hand glimpse of the situation.
Gen. David Petraeus, the top U.S. military commander in Iraq, and U.S. Ambassador to Iraq Ryan Crocker, will return to Washington to testify before the committee next month, providing their assessment of the security and political situations in Iraq.
A detailed itinerary for the Senate delegation has not been released for security reasons -- routine for such visits. However, the senators are slated to meet with Petraeus and Crocker, and Iraqi Prime Minister Nuri al-Maliki.
The senators also will visit Jordan, Israel, Great Britain and France during their trip. E-mail to a friend 
CNN's John King contributed to this report.
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