U.S. President Barack Obama on Thursday night formally accepted the Democratic Party's presidential nomination for a second term, offering his own "harder but better path" to rejuvenate support just two months ahead of the November election.

U.S. President Barack Obama speaks during the Democratic National Convention in Charlotte Sept. 6, 2012. Obama on Thursday night formally accepted the Democratic Party's presidential nomination, offering his own "harder but better path" to rejuvenate support just two months ahead of the November election. [Zhang Jun/Xinhua]

During the prime time speech at the Democratic National Convention, Obama stressed that the nation under his first term is "moving forward."

"I won't pretend the path I'm offering is quick or easy. I never have. You did not elect me to tell you what you wanted to hear. You elected me to tell you the truth. And the truth is, it will take more than a few years for us to solve challenges that have built up over decades," said Obama in his much-anticipated speech.

He asked Americans to "rally around a set of goals" in next four years, a "real plan" focusing on manufacturing, energy, education, national security and deficit cutting.

The goals include to create 100 million new manufacturing jobs by the end of 2016, to double exports by the end of 2014, to cut net oil imports in half by 2020, to cut the growth of college tuition in half over the next 10 years, as well as to reduce the deficit by more than 4 trillion U.S. dollars over the next decade.

"Our path is harder, but it leads to a better place," concluded him.

As it was expected, Obama tried to paint sharp contrast with the Republican challenger Mitt Romney, following efforts by dozens of Democratic speakers during the three-day convention.

Obama took the stage on Thursday night after his running mate Vice President Joe Biden who asked for four more years to complete "a mission we will complete."

Obama's speech also came after the well-received ones of First Lady Michelle Obama and former U.S. President Bill Clinton respectively during the first two days of the convention.

The first lady made quite a rousing speech from a personal perspective trying to boost grassroots' support for her husband while the two-term former President made his best to defend Obama's bid to a second term from Republicans' attacks.

Clinton launched counter-attacks against the Republicans' frequent criticism of Obama over the country's economic woes, saying it was unfair to pin the blame on Obama for the economic ills he inherited four years ago.

"No president, not me, not any of my predecessors, could have fully repaired all the damage that he found in just four years," Clinton said.

Noting that many Americans are still "frustrated" by the current fragile economy, he suggested "too many people do not feel it yet" and more time is needed for pro-growth measures to take effect.

The bad weather forecast also forced Democrats to move Obama's big moment speech indoors from a stadium which could seat over 70,000 backers, making it hard to replicate the overwhelming charisma of Obama's first acceptance speech as Democratic nominee four years ago in an outdoor stadium in Denvor.

The venue for the speech, which was originally planned in Bank of America Stadium, was changed to Time Warner Cable Arena, the site of the 2012 Democratic National Convention of the first two days, a downtown sports and entertainment arena with maximum capacity of 20,000 seats.

Democrats hope the three-day convention would generate a renewed enthusiasm for Obama's re-election bid and help him win the battleground of North Carolina.

Organizers of the convention said nearly 6,000 delegates have attended the convention in Charlotte, the largest city of North Carolina.

Obama and Romney have been virtually deadlocked nationwide, as the presidential campaign geared up to general election. Even the convention would hardly serve as a bump to Obama's support, said the Obama campaign before the convention, trying to downplay expectations.