CASTINE (AP) – Republican Sen. John McCain of Arizona delivered the commencement address Saturday at Maine Maritime Academy, urging the school’s 165 graduates to strive for leadership as they enter the next stage in their lives.

McCain, 68, spoke candidly about his own background in the U.S. Navy, poking fun at his lack of discipline and the many demerits he earned during his 22 years as an officer.

McCain joked that it was quite a privilege for someone who graduated fifth from the bottom of his class in 1958 to be invited to speak at the graduation ceremony.

His remarks turned serious when he talked about the five years he spent in as a prisoner of war in Vietnam, but McCain ended his address by calling upon students to hear the voice in their own hearts.

Prior to the graduation ceremony, McCain and Republican Sen. Susan Collins of Maine spoke briefly to a small group of media members about Social Security and whether or not McCain will pursue the Republican nomination for president in 2008.

McCain, serving his fourth term, lost a battle for the GOP nomination in 2000 to President Bush and was coy in his comments Saturday about making another try. He said no announcement was imminent.

“Senator Collins calls me every morning and every evening and urges me to do so,” McCain said. “But I’m going to wait a couple of years and then make a decision.”

Addressing Social Security, Collins credited the president with tackling a very difficult issue.

“In the long run, Social Security is not sustainable in its present form. That means that we need to look at other ways to ensure that the system is there for our children and grandchildren,” Collins said.

McCain expressed concern that partisanship on the issue could be counterproductive.

Bush made another pitch for his plan to overhaul Social Security on Saturday, this time in his weekly radio address.

His proposals to make the program more solvent include letting workers divert some of their Social Security payroll taxes into private accounts and cutting benefits now promised to future retirees in all but the lowest income brackets.