John McCain, on the first day of a tour intended to tout his security credentials, admitted yesterday that he was caught off guard by the recent violence in Iraq. McCain, who plans to devote the week to showcasing his family's tradition of military service, told reporters in Mississippi that he had not expected the Iraqi leader, Nouri al-Maliki, to launch an offensive against Shia militias in Basra - especially without informing the Americans.

"I just am surprised that he would take it on himself to go down and take charge of a military offensive," he said. "I had not anticipated that he would do that."

It was an unexpected admission for a candidate who has based his campaign around his military credentials. McCain, now the presumptive Republican nominee, was from the start one of the most enthusiastic supporters of the US invasion of Iraq. However, he broke with George Bush in the early days of the war, arguing forcefully for a larger American troop presence.

The visit to Mississippi was the first leg of a week-long tour, meant to remind Americans of the McCain family's four generations of service in the military and his commitment to values of "honour, courage, duty, perseverance and leadership". It also helps to bring McCain positive attention at a time when Hillary Clinton and Barack Obama are in a bruising campaign for the Democratic nomination.

McCain's campaign has started to broadcast television ads dwelling on his years as a prisoner of war in Hanoi.

From Meridien, Mississippi, where there is an airfield named after McCain's grandfather, a former US navy admiral, he heads today for his former high school in Alexandria, Virginia. Tomorrow, McCain will revisit the US naval academy in Annapolis, Maryland, where he graduated fifth from the bottom of his class.

Now 71, McCain claimed yesterday that the period of his life was one of youthful rebellion. "As a boy, my family legacy, as fascinating as it was to me, often felt like an imposition," he said. But he said he came in the end to recognise the importance of service.