CHARLOTTE, N.C. - US first lady Michelle Obama acknowledged on Tuesday that the change her husband Barack Obama sought in his White House campaign four years ago has proven difficult but urged voters to give him another term to fix the weak US economy.

"He reminds me that we are playing a long game here, and that change is hard, and change is slow, and it never happens all at once," she told the Democratic National Convention in Charlotte, North Carolina. "But eventually we get there. We always do," she said.

With Democrats anxious about a race with Republican Mitt Romney that is too close to call nine weeks before the Nov. 6 election, Mrs. Obama urged party activists to rally around the president.

"We must work like never before, and we must once again come together and stand together for the man we can trust to keep moving this great country forward, my husband, our president, Barack Obama," she said.

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