Denver, Colorado - Former president Bill Clinton Wednesday threw his support fully behind Democratic presidential nominee Barack Obama, saying the country needed his strong leadership to rebuild the American economic dream and "restore America's leadership in the world."

Clinton's speech came just hours after Democratic delegates formally nominated Obama on the third night of the presidential convention - a prize that narrowly eluded his wife, Senator Hillary Clinton, during the primary election battle.

The Clintons, popular party luminaries, have tried to put aside the idea that they are bitter over Hillary's loss, and to create a swell of party unity as the campaign heads into the backstretch before the November 4 elections.

Yet Obama's campaign is wary of how to deploy Bill Clinton in the general election campaign after being at the wrong end of Clinton's sharp tongue during the hard-fought primary elections.

On Tuesday, Senator Clinton delivered an emotional bid for her diehard supporters to get behind Obama. Earlier Wednesday evening, she helped orchestrate and made the final bid for Obama's nomination by acclamation.

Joking that her speech was a tough act to follow, the former president added his voice of acclaim for the party's first African- American candidate, saying he was convinced Obama had the "remarkable ability to inspire" and the "intelligence and curiosity" necessary to be president.

Clinton said Obama's "long hard primary" against Hillary had "tested and strengthened him."

"Barack Obama is ready to lead America and restore American leadership in the world," Clinton said, triggering a round of cheering.

"He has shown a clear grasp of our foreign policy and national security challenges, and a firm commitment to rebuild our badly strained military," Clinton said. "He will choose diplomacy first and military force as a last resort."

Clinton sounded the dual themes of failed diplomacy and falling economy against US President George W Bush and presumptive Republican candidate John McCain, which have dominated the four-day convention at Denver's Pepsi center.

"Our position in the world has been weakened by too much unilateralism and too little cooperation, by a perilous dependence on imported oil" and a refusal to "lead on global warming," Clinton charged.

The former president defended Obama against Republican attacks on his lack of experience, recalling how 16 years ago, Republicans had said he also had been too young and too inexperienced to be commander-in-chief.

The theme of the evening was "securing America's future" and Clinton, who had to outshout the enthusiastic crowd three times to get started on his speech, said he was also there to "warm up the crowd" for Joe Biden - Obama's vice presidential choice who has added a strong suit in foreign policy to the centre-left Democrats' campaign.

"With Joe Biden's experience and wisdom, supporting Barack Obama's proven understanding, insight and good instincts, America will have the national security leadership we need," he said. (dpa)