Obama, McCain spar over Social Security

* Obama links McCain to Bush's Social Security plan

* McCain denies he is for privatization

* Two nominees to make rare joint appearance to mark 9/11

By Deborah Charles

TERRE HAUTE, Ind., Sept 6 (Reuters) - Democratic presidential nominee Barack Obama warned the elderly on Saturday that Republican rival John McCain would put their retirement income in danger.

Obama told a Washington gathering of AARP, an interest group that represents the elderly, that McCain would go beyond President George W. Bush's rejected plan to allow people to invest some of their Social Security funds.

Obama said McCain has embraced that proposal, called privatizing, and "gone even further, suggesting that the best answer to the growing pressures on Social Security might be to cut cost-of-living adjustments or raise the retirement age."

"I will not do either," he said in remarks delivered to the group by satellite from Newark, New Jersey, trying again to link McCain with the unpopular president.

McCain, a senator from Arizona who got the Republican presidential nomination this week in St. Paul, Minnesota, denied he favored privatizing, saying, "No proposal of mine would affect any retiree in any way and nothing would be mandatory."

"We're not going to privatize it," he told the same group later by satellite. "It is a government function to provide for those who have worked and earned and saved all their lives."

"But we want to give, if we can, younger workers the option of taking some of their own money and the option to put it into an account with their name on it."

In his hard-fought nominating campaign, Obama lost the elderly vote to New York Sen. Hillary Clinton. That voting bloc is considered one of the areas where Clinton excelled that Obama needs to win over.

McCain, who at 72 would be the oldest person first elected president, ran well among the elderly in his Republican primary campaign for the nomination.

JOINT APPEARANCE

Now that the nominating conventions are over, the candidates have less than two months until the Nov. 4 election to make their case to the American public.

But the two nominees will put their politicking aside on Thursday when they make a rare joint appearance at the site of the destroyed World Trade Center in New York to commemorate those who died in the attacks on Sept. 11, 2001.

There was no letup on Saturday, though. Obama, an Illinois senator who would be the country's first black president, criticized McCain and the Republicans for not discussing issues or offering an outline for the future at their convention, which ended on Thursday night.

"He's not offering much change, that's why you didn't hear much about his plans for the future this week," Obama told the AARP.

He said his whole campaign was about the future "and securing your future starts with protecting Social Security -- today, tomorrow and forever."

Social Security provides a monthly check to the country's elderly and disabled. Obama said more than half of seniors depend on it for more than half of their income.

Later Obama mocked McCain's claim to be the agent of change at a rally in Terre Haute, Indiana, a Republican leaning state that Democrats think they can win this year.

"This is coming from the party that's been in charge for eight years," he said. "They've been running the show. Been up in the White House. John McCain brags -- 90 percent of the time I've voted with George Bush ... and suddenly he's the change agent."

At his rally in Colorado Springs, Colorado -- another state Democrats hope to take from Republicans -- McCain insisted it was he and his running mate, Alaska Gov. Sarah Palin, were the ones with the reputations for shaking things up.

Palin pointed to her Democratic counterpart, six-term Sen. Joe Biden of Delaware, as a man with "many chairmanships across many, many years in Washington and certainly many friends in the Washington establishment" but not an agent of change.

With the campaign going full tilt, Obama, McCain and Biden all scheduled appearances on the Sunday television talk show circuit. Only Palin was not scheduled. Since she was made the surprise pick for the No. 2 spot a week ago she has not given any media interviews. (Additional reporting by Jeff Mason; Writing by David Wiessler; Editing by Anthony Boadle)