(Updates with suicide bombing, Cheney quotes)
By Tabassum Zakaria
BAGHDAD, March 17 (Reuters) - U.S. Vice President Dick Cheney on Monday declared the 2003 U.S.-led invasion of Iraq a "successful endeavour" in a visit to Iraq that was overshadowed by a suicide bombing that killed at least 25 people.
"If you look back on those five years it has been a difficult, challenging but nonetheless successful endeavour ... and it has been well worth the effort," Cheney told a news conference in Baghdad after meeting Iraqi leaders.
The Iraq war is a major issue in the U.S. presidential campaign. As it enters it sixth year, the war has cost the U.S. economy $500 billion and seen nearly 4,000 U.S. soldiers and tens of thousands of Iraqis killed.
Shortly after Cheney spoke, a woman wearing a suicide vest blew herself up in a cafe in the southern holy Shi‘ite city of Kerbala, killing 25 people and wounding 50, police and health officials said. Bombs in Baghdad killed four and wounded 13.
Cheney, an architect of the invasion, arrived as Republican presidential candidate John McCain was meeting Iraqi leaders as part of a Senate Armed Services Committee fact-finding mission.
"I was last in Baghdad 10 months ago and I sense that, as a result of the progress that has been made since then, phenomenal changes in terms of the overall situation," Cheney said after meeting Iraqi Prime Minister Nuri al-Maliki.
Cheney said there had been a "remarkable turnaround" in security after 30,000 extra troops were sent to Iraq last year to help reduce sectarian violence that threatened civil war.
Despite the improved security, however, some 4 million Iraqis are still displaced, and the International Committee of the Red Cross said in a report on Monday that millions were still deprived of clean water and medical care.
Like McCain, Cheney is in Iraq as part of a wider tour to the Middle East. Cheney will also visit Saudi Arabia, Jerusalem, the Palestinian territories, Turkey and Oman on a nine-day tour.
Both men have been staunch supporters of the U.S. troop build-up that Washington says helped drag Iraq back from the brink of all-out sectarian civil war between majority Shi‘ites and minority Sunni Muslims who were dominant under Saddam.
"The surge is working," McCain, referring to the troop build-up, told CNN in an interview in Baghdad.
(Writing by Paul Tait and Ross Colvin, additional reporting by Sami al-Jumaili in Kerbala; Editing by Richard Balmforth)