WASHINGTON — Former New York mayor Rudy Giuliani urged polarized Americans on Thursday to "rediscover our unity" as he prepared to mark ten years since the September 11th attacks with a national speech.

"We withstood the worst attack of our history, intended by our enemies to destroy us. Instead, it drew us closer and made us more united," he said in a statement, warning: "It's a strength that must be guarded and nurtured."

"We must rediscover our unity," said Giuliani, whose take-charge response to the attacks made him a national figure during an all-too-brief period in which superheated partisan rhetoric cooled in the shadow of the tragedy.

Giuliani will deliver the Republican party's weekly address -- typically a response to US President Barack Obama's own brief Saturday speeches -- said Republican Senate Minority Leader Mitch McConnell.

"I can't think of a better person than former New York Mayor Rudolph Giuliani to offer his perspective on that dark day in American history and pay tribute to the victims and heroes of that disaster," said McConnell.

Obama was to attend a commemorative concert at Washington's Kennedy Center on Sunday and make remarks as Americans mourn those lost when Al-Qaeda extremists flew hijacked airliners into the World Trade Center and the Pentagon.